intrinsic-factor and Anemia--Megaloblastic

Vitamin B12 is assimilated and transported by complex mechanisms that involve three transport proteins, intrinsic factor (IF), haptocorrin (HC) and transcobalamin (TC) and their respective membrane receptors. Vitamin deficiency is mainly due to inadequate dietary intake in vegans, and B12 malabsorption is related to digestive diseases. This review explores the physiology of vitamin B12 absorption and the mechanisms and diseases that produce malabsorption. In the stomach, B12 is released from food carrier proteins and binds to HC. The degradation of HC by pancreatic proteases and the pH change trigger the transfer of B12 to IF in the duodenum. Cubilin and amnionless are the two components of the receptor that mediates the uptake of B12 in the distal ileum. Part of liver B12 is excreted in bile, and undergoes an enterohepatic circulation. The main causes of B12 malabsorption include inherited disorders (Intrinsic factor deficiency, Imerslund-Gräsbeck disease, Addison's pernicious anemia, obesity, bariatric surgery and gastrectomies. Other causes include pancreatic insufficiency, obstructive Jaundice, tropical sprue and celiac disease, bacterial overgrowth, parasitic infestations, Zollinger-Ellison syndrome, inflammatory bowel diseases, chronic radiation enteritis of the distal ileum and short bowel. The assessment of B12 deficit is recommended in the follow-up of subjects with bariatric surgery. The genetic causes of B12 malabsorption are probably underestimated in adult cases with B12 deficit. Despite its high prevalence in the general population and in the elderly, B12 malabsorption cannot be anymore assessed by the Schilling test, pointing out the urgent need for an equivalent reliable test.

Topics: Adult; Aged; Anemia, Megaloblastic; Humans; Intrinsic Factor; Malabsorption Syndromes; Male; Vitamin B 12; Vitamin B 12 Deficiency

In our pioneering work in 1956, two binders of vitamin B12 (B12) alias cobalamin (Cbl) were identified in gastric juice, S with slow electrophoretic mobility, a 70 kD protein with intrinsic factor (IF) activity and another rapid (R), not IF active but probable digestion product. Numerous sources contained a protein immunologically identical to R (haptocorrin, Hc). Another IF-active component (I) was found. Isoelectric focusing showed that S, I and R were assemblies of "isoproteins" with different pI's due to varying glycosidation. Isolation of S, I and R in microquantities was achieved in 1962 using a series of ion exchange chromatographies and gel filtration. Ponderable products were obtained in 1965-1966. The B12-IF complex was a dimer, contained 13% carbohydrate and showed a different absorption spectrum than B12. Using the Schilling test, B12 absorption was shown to require Ca(++), bound in vitro to the ileal receptor and IF, but most of Ca(++) could be removed with sialidase. The receptor-substrate complex contained Ca(++) and carbohydrate. The purified receptor was shown to contain two main subunits. The Imerslund-Gräsbeck syndrome was discovered 1958-1960; it is caused by mutations in either of two genes, cubilin or amnionless, which form the multiligand receptor cubam. Testicular biopsies during and after B12-treated deficiency showed remarkable improvement after therapy. Studies of the turnover of radioactive B12 revealed biliary and fecal excretion, enterohepatic circulation and allowed calculation of biological half-life and daily need. The B12 coenzymes largely behaved like B12. To study whether radiocobalt in B12 was representative of the rest of the B12 molecule, (32)P and (57)Co labeled hydroxocobalamins were biosynthesized and shown to behave identically when given simultaneously to rats. The complex metabolism of B12 explains the pathogenesis of B12 deficiencies. Some of its mechanisms are not restricted to B12, e.g. the endocytosis of B12-IF also applies to other macromolecules.

Topics: Anemia, Megaloblastic; Animals; Gastric Juice; Humans; Intrinsic Factor; Malabsorption Syndromes; Proteinuria; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Anemia, Megaloblastic; Humans; Intrinsic Factor; Nervous System Diseases; Vitamin B 12; Vitamin B 12 Deficiency

This review focusses on research performed by the author and coworkers. The absorption, turnover and excretion of cobalamin and the pathogenesis of cobalamin deficiency states are described and the laboratory tests used to diagnose these states are discussed. Topics dealt with in detail include: overall turnover, daily need, enterohepatic circulation and excretion of cobalamin and other corrins . The soluble proteins mediating cobalamin transport and their cellular receptors are described and their nomenclature, isolation, structure and mode of action, the role of calcium in the membrane transport, the evolution of these systems and the analogies with transport systems for other substrates are discussed together with deficiency states, especially fish tapeworm anemia and familial selective vitamin B12 malabsorption with proteinuria. Folate deficiency is a relatively rare cause of megaloblastic anemia in Scandinavia but common in North America and explanations for this difference are suggested. The methods of assaying cobalamin in serum and plasma and the performance of radiovitamin B12 absorption tests are critically evaluated. The measurement of intrinsic factor in gastric juice, serum, amniotic fluid and urine is described.

Topics: Anemia, Megaloblastic; Anemia, Pernicious; Biological Transport; Corrinoids; Diet; Diphyllobothriasis; Endocytosis; Erythrocyte Indices; Folic Acid; Humans; Intestinal Absorption; Intrinsic Factor; Malabsorption Syndromes; Membrane Transport Proteins; Metabolic Clearance Rate; Receptors, Cell Surface; Receptors, Peptide; Transcobalamins; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Antibodies; Cobalt Radioisotopes; Deoxyuridine; Folic Acid; Humans; Intestinal Absorption; Intrinsic Factor; Isotope Labeling; Protein Binding; Radioimmunoassay; Transcobalamins; Vitamin B 12

Topics: Adolescent; Adult; Anemia, Hemolytic; Anemia, Macrocytic; Anemia, Megaloblastic; Anemia, Pernicious; Biological Transport; Bone Marrow; Bone Marrow Cells; Child; Child, Preschool; Female; Folic Acid; Folic Acid Deficiency; Homocystinuria; Humans; Infant; Intrinsic Factor; Malabsorption Syndromes; Male; Metabolism, Inborn Errors; Methionine; Methionine Adenosyltransferase; Orotic Acid; Phenylketonurias; Tetrahydrofolate Dehydrogenase; Transcobalamins; Vitamin B 12

1. Low serum B12 levels can be measured with considerable precision by microbiological assay with the Euglena gracilis assay and B12 deficiency can be recognised with a high level of consistency by either the Euglena or L. leichmannii assays. Either method is ideally suited for the assay of large numbers of specimens. The Lactobacillus leichmanii technique requires preliminary extraction of protein and it has been suggested that this may be a source of inaccuracy. 2. The radioisotope dilution assay should be the ideal method of measuring B12 levels in small or moderate numbers of specimens for it is a simple method that can be carried out in any laboratory with suitable counting equipment. After many false starts the conditions required for accurate assay are now understood. Each of 40 to 50 radioisotopic dilution techniques that have been introduced claims to be capable of differentiating B12 deficiency from control subjects but the reported correlations between the actual levels found in the two different assays are variable and the levels may be much higher with some radioisotopic methods. 3. The subnormal serum levels which are found in pernicious anaemia with all these techniques indicate severe reduction of the liver B12 level. A low serum B12 level in other conditions has, in the absence of associated folate or iron deficiency, the same significance. If the fall in the serum B12 level is associated with folate or iron deficiency, the tissue B12 levels are usually reduced but not to the low levels found in B12 deficiency states. 4. In practice, a subnormal B12 level is a valuable pointer not only to unsuspected pernicious anaemia but also to other gastrointestinal or nutritional disorders. The significance of a fall in the B12 level can only be understood if its cause is defined by a full clinical and gastroenterological investigation. 5. Falsely low serum B12 levels are found under certain iatrogenic conditions and B12 levels may be normal in spite of cellular deficiency of B12 under the rare circumstances of pernicious anaemia being associated with chronic myeloid leukaemia or when there is deficiency of TC 2.

Topics: Anemia, Megaloblastic; Anemia, Pernicious; Ascorbic Acid; Biological Assay; Bone Marrow; Bone Marrow Cells; Carrier Proteins; Deoxyuridine; Euglena gracilis; Female; Folic Acid Deficiency; Humans; Intrinsic Factor; Lactobacillus; Leukemia, Myeloid; Male; Pregnancy; Pregnancy Complications; Radioisotope Dilution Technique; Transcobalamins; Vitamin B 12; Vitamin B 12 Deficiency

Inherited malabsorption of cobalamin (Cbl) causes hematological and neurological abnormalities that can be fatal. Three genes have been implicated in Cbl malabsorption; yet, only about 10% of ~400-500 reported cases have been molecularly studied to date. Recessive mutations in CUBN or AMN cause Imerslund-Gräsbeck Syndrome (IGS), while recessive mutations in GIF cause Intrinsic Factor Deficiency (IFD). IGS and IFD differ in that IGS usually presents with proteinuria, which is not observed in IFD. The genetic heterogeneity and numerous differential diagnoses make clinical assessment difficult.. We present a large genetic screening study of 154 families or patients with suspected hereditary Cbl malabsorption. Patients and their families have been accrued over a period spanning >12  years. Systematic genetic testing of the three genes CUBN, AMN, and GIF was accomplished using a combination of single strand conformation polymorphism and DNA and RNA sequencing. In addition, six genes that were contenders for a role in inherited Cbl malabsorption were studied in a subset of these patients.. Our results revealed population-specific mutations, mutational hotspots, and functionally distinct regions in the three causal genes. We identified mutations in 126/154 unrelated cases (82%). Fifty-three of 126 cases (42%) were mutated in CUBN, 45/126 (36%) were mutated in AMN, and 28/126 (22%) had mutations in GIF. We found 26 undescribed mutations in CUBN, 19 in AMN, and 7 in GIF for a total of 52 novel defects described herein. We excluded six other candidate genes as culprits and concluded that additional genes might be involved.. Cbl malabsorption is found worldwide and genetically complex. However, our results indicate that population-specific founder mutations are quite common. Consequently, targeted genetic testing has become feasible if ethnic ancestry is considered. These results will facilitate clinical and molecular genetic testing of Cbl malabsorption. Early diagnosis improves the lifelong care required by these patients and prevents potential neurological long-term complications. This study provides the first comprehensive overview of the genetics that underlies the inherited Cbl malabsorption phenotype.

Topics: Anemia, Megaloblastic; Ethnicity; Female; Founder Effect; Genetic Association Studies; Genetic Heterogeneity; Genetic Testing; Humans; Intrinsic Factor; Malabsorption Syndromes; Male; Membrane Proteins; Mutation; Proteins; Proteinuria; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Anemia, Megaloblastic; Anemia, Pernicious; Autoantibodies; Autoimmune Diseases; Folic Acid Deficiency; Gastritis, Atrophic; Humans; Intrinsic Factor; Parietal Cells, Gastric; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Administration, Oral; Anemia, Megaloblastic; Anemia, Pernicious; Antibodies; Folic Acid; Folic Acid Deficiency; Humans; Injections, Intramuscular; Intrinsic Factor; Leucovorin; Schilling Test; Vitamin B 12; Vitamin B Complex

A 4-base deletion has been identified in the coding region of the gene for gastric intrinsic factor (IF) in an 11-year-old girl with severe anemia and cobalamin (Cbl) deficiency. The bone marrow showed frank megaloblastic morphology, and the Schilling test indicated a failure to absorb Cbl that was corrected by coadministration of IF. Pentagastrin administration induced acid secretion, but the gastric juice lacked IF as determined by CbI binding, by fractionation of protein-bound CbI, and by immunoprecipitation with anti-IF antiserum. Individual exons were amplified by the polymerase chain reaction by using primers to the flanking intronic regions, and the nucleotide sequence analysis identified a 4-base deletion (c183_186delGAAT) spanning positions 104 to 107 in exon 2, resulting in premature termination of translation. This mutation also eliminates a site for Bst XI endonuclease and introduces a site for BsaBI for identifying this deletion in hereditary IF deficiency.

Topics: Anemia, Megaloblastic; Child; Female; Gastric Juice; Gene Deletion; Humans; Intrinsic Factor; Pentagastrin; Vitamin B 12; Vitamin B 12 Deficiency

We present a case of extreme pancytopenia in a 27-year-old pregnant woman. The initial picture was compatible with a severe hematological problem in the category of aplastic anemia, paroxysmal nocturnal hemoglobinuria or even acute leukemia. The further biochemical investigations revealed, however, a folate deficiency. Nowadays this is a very rare cause of pancytopenia. Next to this she also had a Vitamin B(12) deficiency due to intrinsic factor failure. The recent literature is discussed.

Topics: Adult; Anemia, Megaloblastic; Blood Transfusion; Bone Marrow; Female; Folic Acid; Folic Acid Deficiency; Humans; Infant, Newborn; Intrinsic Factor; Male; Pancytopenia; Platelet Transfusion; Pregnancy; Pregnancy Complications; Pregnancy Outcome; Vitamin B 12; Vitamin B 12 Deficiency

Megaloblastic anemia 1 (MGA1) is an autosomal recessive disorder caused by the selective intestinal malabsorption of intrinsic factor (IF) and vitamin B(12)/cobalamin (Cbl) in complex. Most Finnish patients with MGA1 carry the disease-specific P1297L mutation (FM1) in the IF-B(12) receptor, cubilin. By site-directed mutagenesis, mammalian expression, and functional comparison of the purified wild-type and FM1 mutant forms of the IF-Cbl-binding cubilin region (CUB domains 5-8, amino acid 928-1386), we have investigated the functional implications of the P1297L mutation. Surface plasmon resonance analysis revealed that the P1297L substitution specifically increases the K(d) for IF-Cbl binding several-fold, largely by decreasing the association rate constant. In agreement with the binding data, the wild-type protein, but not the FM1 mutant protein, potently inhibits 37 degrees C uptake of iodine 125-IF-Cbl in cubilin-expressing epithelial cells. In conclusion, the data presented show a substantial loss in affinity of the FM1 mutant form of the IF-Cbl binding region of cubilin. This now explains the malabsorption of Cbl and Cbl-dependent anemia in MGA1 patients with the FM1 mutation. (Blood. 2000;96:405-409)

Topics: Anemia, Megaloblastic; Binding Sites; Cloning, Molecular; Gene Expression; Humans; Intrinsic Factor; Membrane Glycoproteins; Mutagenesis, Site-Directed; Mutation; Polymerase Chain Reaction; Receptors, Cell Surface; Structure-Activity Relationship; Surface Plasmon Resonance; Transfection; Vitamin B 12

Topics: Adolescent; Adult; Anemia, Megaloblastic; Child; Female; Humans; Intrinsic Factor; Malabsorption Syndromes; Male; Middle Aged; Receptors, Cell Surface; Reference Values; Vitamin B 12

Uptake of vitamin B12 (cyanocobalamin) is facilitated by the cobalamin-binder gastric intrinsic factor (IF), which recognizes a 460-kD receptor, cubilin, present in the epithelium of intestine and kidney. Surface plasmon resonance analysis of ligand-affinity-purified human cubilin demonstrated a high-affinity calcium- and cobalamin-dependent binding of IF-cobalamin. Complete cDNA cloning of the human receptor showed a 3597 amino acid peripheral membrane protein with 69% identity to rat cubilin. Amino-terminal sequencing of the receptor indicates that the cDNA sequence encodes a precursor protein undergoing proteolytic processing due to cleavage at a recognition site (Arg7-Glu8-Lys9-Arg) for the trans-Golgi proteinase furin. Using fluorescence in situ hybridization, radiation hybrid mapping, and screening of YAC clones, the human cubilin gene was mapped between the markers D10S1661 and WI-5445 on the short arm of chromosome 10. This is within the autosomal recessive megaloblastic anemia (MGA1) 6-cM region harboring the unknown recessive-gene locus of juvenile megaloblastic anemia caused by intestinal malabsorption of cobalamin (Imerslund-Gräsbeck's disease). In conclusion, the present molecular and genetic information on human cubilin now provides circumstantial evidence that an impaired synthesis, processing, or ligand binding of cubilin is the molecular background of this hereditary form of megaloblastic anemia.

Topics: Amino Acid Sequence; Anemia, Megaloblastic; Animals; Chromosome Mapping; Chromosomes, Artificial, Yeast; Chromosomes, Human, Pair 10; DNA, Complementary; Furin; Genes; Genes, Recessive; Humans; Hybrid Cells; In Situ Hybridization, Fluorescence; Intrinsic Factor; Kidney Cortex; Molecular Sequence Data; Polymerase Chain Reaction; Rats; Receptors, Cell Surface; Sequence Homology, Amino Acid; Species Specificity; Subtilisins; Swine; Vitamin B 12

A case of 78-year old man with megaloblastic anemia occurring 20 years after partial gastrectomy is reported. Since about 2 years earlier he had an episode of convulsion, and he had been on anti-convulsants (diphenylhydantion, phenobarbital) until admission. Physical examination revealed a pale lean man with polyneuropathy and mental impairment. Laboratory findings revealed WBC 3100/microliters, RBC 187 X 10(4)/microliters, HB 7.9 g/dl, MCV 124.4 microns3, MCH 42.7 micrograms, platelet counts 15.7 X 10(4)/microliters, serum vitamin B12 (VB12) 380 pg/ml, and serum folic acid 5.1 ng/ml. Serum autoantibodies to intrinsic factor (IF) and parietal cells were positive. Bone marrow examination revealed erythroid hyperplasia and megaloblastic changes. Schilling test revealed impaired absorption of VB12 with or without IF, but X-ray study of the small bowels was unremarkable. Treatment with intramuscular cyanocobalamin resulted in a rapid clinical improvement. A repeat Schilling test after 4 months of therapy showed a normal VB12 absorption in the presence of IF. These findings suggest that VB12 malabsorption of the 1st Schilling test was due to intestinal dysfunction caused by the VB12 deficiency state itself, and the improvement of VB12 absorption with IF after therapy suggests a pathogenesis similar to pernicious anemia in this patient.

Topics: Aged; Anemia, Macrocytic; Anemia, Megaloblastic; Autoantibodies; Gastrectomy; Humans; Intrinsic Factor; Male; Postoperative Complications; Schilling Test; Vitamin B 12

Coexisting deficiencies of both intrinsic factor (IF) and R binder were identified in an Algerian boy who presented with severe megaloblastic anemia, growth retardation, and neurologic dysfunction with typical features of subacute combined degeneration of the spinal cord. The anemia responded completely to cyanocobalamin and folic acid. IF was absent from gastric juice, but acid secretion and gastric mucosa were normal. R binders were absent from gastric juices as well as from serum, saliva, and polymorphonuclear leukocytes. The patient's father exhibited absence of R binder in his serum with a low serum vitamin B12 level and was asymptomatic. This unique case of simultaneous IF and R binder deficiencies suggests a genetic association between these two functionally and immunologically dissimilar, but structurally close vitamin B12-binding proteins.

Topics: Adolescent; Anemia, Megaloblastic; Gastric Juice; Growth Disorders; Humans; Intrinsic Factor; Male; Pedigree; Saliva; Spinocerebellar Degenerations; Transcobalamins

Three familial cases of congenital intrinsic factor deficiency are reported: the stress is put on the interest of gastric investigations and especially of the quantity of intrinsic factor in the gastric juice when investigating megaloblastic anemia due to vitamin B12 deficiency. The study of the level of intrinsic factor in the gastric juice is proposed as a test for identifying carriers.

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Child, Preschool; Female; Gastric Juice; Genetic Carrier Screening; Humans; Infant; Intrinsic Factor; Vitamin B 12 Deficiency

The results of an Interregional quality assurance scheme for tests in the diagnosis of megaloblastic anaemia were reviewed to assess the methods used. Serum folate assays showed great variation between methods, partly due to limitations in assessment by external quality assurance. Red cell folate assays yielded widely different results and much imprecision due both to the differences in preparation of the haemolysate and to the problems inherent in radioassay of a mixture of folate compounds. Intrinsic factor antibody tests showed appreciable variation in sensitivity. There was considerable inconsistency in the detection of polymorph nuclear hypersegmentation.

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Antibodies; Erythrocytes; Folic Acid; Humans; Intrinsic Factor; Laboratories; Methods; Neutrophils; Quality Control; Vitamin B 12

A middle-aged woman developed a postgastric bypass megaloblastic anemia which responded to treatment. She eventually had the bypass reversed 6 1/2 yr after it had been performed. Gastric parietal cell function has remained abnormal almost 3 yr after reversal of the bypass, as demonstrated by abnormal Schilling tests and high serum gastrin levels. Parietal cell antibodies in high titer, but no intrinsic factor antibodies, were demonstrated in her blood. These observations are interpreted as indicating the development of irreversible chronic atrophic gastritis probably related to reflux of bile into the bypassed stomach.

Topics: Adult; Anemia, Megaloblastic; Female; Gastric Acid; Gastrins; Humans; Intrinsic Factor; Parietal Cells, Gastric; Postoperative Complications; Stomach; Vitamin B 12 Deficiency

Lymphocyte subpopulations and intrinsic factor and gastric parietal cell antibodies have been measured in 23 patients with megaloblastic anaemia who responded to treatment with hydroxocobalamin. The ratio of helper (OKT4) to suppressor (OKT8) lymphocytes was significantly increased in patients with intrinsic factor antibody compared with those who lacked the antibody. No such correlation was found for gastric parietal cell antibody. Alterations in the lymphocyte helper to suppressor (OKT4:OKT8) ratio may be associated with pernicious anaemia.

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Antibodies, Monoclonal; Autoantibodies; Humans; Hydroxocobalamin; Intrinsic Factor; Leukocyte Count; Lymphocytes; Parietal Cells, Gastric; T-Lymphocytes, Helper-Inducer; T-Lymphocytes, Regulatory

Three siblings presented in their second year of life with megaloblastic anemia that responded to parenteral cobalamin (Cbl). Schilling tests were less than 1%, correcting to 5 to 15% after addition of hog intrinsic factor (IF). Gastric acid analysis and gastric biopsies were normal by light and electron microscopy. Gastric juice contained less than 3 pmol/ml of Cbl-binding ability due to IF (normal, 10-34 pmol/ml) and less than 2 pmol/ml of IF when measured with a radioimmunoassay (RIA) using normal human IF-[57Co]Cbl and rabbit anti-human IF serum (normal, 17-66 pmol/ml). However, RIA employing rabbit anti-hog IF serum gave values of 4-13 pmol/ml of IF (normal, 11-33 pmol/ml). This material had an apparent molecular weight of 40,000 (normal IF = 70,000). The IF from gastric biopsies appeared normal in terms of Cbl-binding ability, ileal binding, molecular weight, and both RIAs. This IF differed from normal mucosal IF, in that it lost its Cbl-binding ability when incubated at 37 degrees C at acid pH or in the presence of pepsin or trypsin. This loss was retarded when [57Co]Cbl was bound to the IF before these incubations. The stabilizing effects of neutralization and Cbl were also demonstrated in vivo. Schilling tests for the siblings of 0.4, 0.5, and 1.0% increased to 2.7, 5.7, and 4.3% (P less than 0.05), respectively, when the Schilling tests were repeated with the addition of NaHCO3 and cobinamide (which allows Cbl to bind immediately to IF). We conclude that Cbl malabsorption in these children is due to an abnormal IF that is markedly susceptible to acid and proteolytic enzymes which cause a decrease in its molecular weight and Cbl-binding ability and a loss of antigenic determinants that are recognized by the anti-human IF serum.

Topics: Anemia, Megaloblastic; Child; Child, Preschool; Gastric Juice; Gastric Mucosa; Humans; Hydrogen-Ion Concentration; Intestinal Absorption; Intrinsic Factor; Molecular Weight; Peptide Hydrolases; Vitamin B 12

The first case of megaloblastic anemia due to selective malabsorption of vitamin B(12) and vitamin B(12)-intrinsic factor is described in an otherwise normal female adult, in whom pernicious anemia had previously been diagnosed.

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Female; Humans; Ileum; Intrinsic Factor; Vitamin B 12

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Diagnosis, Differential; Female; Humans; Infant; Intrinsic Factor

A new solid phase vitamin B12 assay is described using intrinsic factor to measure microbiologically-available B12 and R-binder to measure total B12. The solid phase reagent consists of intrinsic factor coupled to polyacrylamide beads and salivary R-binder coupled to polyacrylamide beads. The assay is simple to perform and separates completely sera from controls and patients with megaloblastic anaemia due to B12 deficiency.

Topics: Acrylic Resins; Anemia, Megaloblastic; Humans; Hydrogen-Ion Concentration; Intrinsic Factor; Light; Methods; Nuclear Proteins; Nucleoproteins; Osmolar Concentration; Time Factors; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Autoantibodies; Deoxyuridine; Erythrocyte Indices; Folic Acid; Humans; Intrinsic Factor; Reagent Kits, Diagnostic; Schilling Test; Vitamin B 12

Topics: Adolescent; Anemia, Megaloblastic; Child; Child, Preschool; Female; Folic Acid Deficiency; Humans; Infant; Intestinal Absorption; Intrinsic Factor; Male; Transcobalamins; Vitamin B 12 Deficiency

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Gastrectomy; Humans; Intrinsic Factor; Nutrition Disorders

A ligand assay specific for cobalamin that uses mouse stomach as the source of intrinsic factor has been developed. When mouse stomach extract incubated with radiocobalamin is fractionated by gel chromatography, the radioactive complex elutes as a single peak with apparent molecular weight of 54,900. Formation of the complex is greater than 98% inhibited by human anti-intrinsic factor antibody. When the equivalent of 10,000 pg/ml of cobinamide is added to serum, the apparent cobalamin concentration detected averages 8.5 pg/ml. Correlation with the Lactobacillus leichmannii microbiologic assay results in the regression equation y = 0.97x + 20. In six patients who had megaloblastic anemia the serum cobalamin by the mouse intrinsic factor ligand assay ranged from 0 to 9 pg/ml. Because the primary source of intrinsic factor is free of R proteins, there is no need for extensive purification of the extract. The assay is sensitive, precise, and accurate, and no more difficult to perform than other conventional ligand assay procedures.

Topics: Anemia, Megaloblastic; Animals; Antibodies; Chromatography, Gel; Humans; Intrinsic Factor; Lactobacillus; Mice; Protein Binding; Radioligand Assay; Saliva; Stomach; Vitamin B 12

The megaloblastic anaemia observed in patients with chronic atrophic gastritis is usually due to malabsorption of vitamin B12. In some cases, the absence of intrinsic factor supports the diagnosis of pernicious anaemia but other factors, the importance of which varies from case to case, are also involved. They include proliferation of bacteria in the lumen of the gut, intestinal cell abnormalities resulting from lack of vitamin B12 and low hydrochloric acid output with subsequent reduction in the release of vitamin B12 from foodstuffs. With regard to treatment, it would seem justified to combine oral broad-spectrum antibiotics with parenteral administration of vitamin B12.

Topics: Achlorhydria; Aged; Anemia, Megaloblastic; Female; Gastritis; Gastritis, Atrophic; Humans; Intestine, Small; Intrinsic Factor; Malabsorption Syndromes; Male; Middle Aged; Vitamin B 12 Deficiency

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Anemia, Pernicious; Bone Marrow Cells; DNA; Ferritins; Folic Acid Deficiency; Intestinal Mucosa; Intrinsic Factor; Iron; Myelin Sheath; Schilling Test; Vitamin B 12 Deficiency

Myasthenia gravis (MG) is an autoimmune disease often associated with other autoimmune disorders. A case history of MG with a coexisting atypical megaloblastic anaemia with vitamin B12 deficiency and anti Intrinsic Factor (IF) antibodies, led to a study of humoral and cellular immunity to IF in 81 MG patients. Within this series, 3 other patients had a disturbed humoral and cellular immunity to IF. These 3 patients presented no other features of pernicious anaemia. The possible origins and significance of the anti IF antibodies in MG patients are discussed.

Topics: Adolescent; Adult; Aged; Anemia, Macrocytic; Anemia, Megaloblastic; Antibodies; Antibody Formation; Child; Female; Humans; Immunity, Cellular; Immunologic Techniques; Intrinsic Factor; Male; Middle Aged; Myasthenia Gravis; Vitamin B 12 Deficiency

The definitive diagnosis of pernicious anaemia (PA) in the elderly is by no means always straightforward, particularly when inappropriate medication has been introduced before the institution of specific investigatory procedures. A detailed haematological study was carried out on 301 patients aged 60-95 with a serum B(12) concentration at the laboratory's lower level of normal of 150 ng per litre (Euglena gracilis assay). The diagnosis of PA was based on strict predetermined haematological criteria. All patients were subsequently studied by the simultaneous oral administration of the dual isotopes (57)Co-labelled B(12) bound to intrinsic factor and free (58)Co-labelled B(12) (Dicopac test), and urine was collected over 24 hours after an intramuscular dose of 1 mg nonradioactive B(12) for estimation of the (57)Co/(58)Co B(12) ratio; 255 patients satisfied all criteria for final analysis. The Radiochemical Centre, Amersham suggests an upper limit of the normal range for the (57)Co/(58)Co ratio of 1.3 with a lower limit for PA of 2.0. We were unable to show a sharp borderline in the (57)Co/(58)Co B(12) ratio between those patients shown by other criteria to have PA and those who do not have PA; 34% of the 71 established patients had a ratio below 2.0. From our series a ratio borderline drawn at 1.4 gave only one false negative (1.4% of the PA group). Of the 175 non-PA cases, nine (5%) gave false positive results; four of these had (58)Co excretion levels high enough to make misdiagnosis unlikely. In a proportion of patients the (57)Co/(58)Co B(12) ratio was estimated at regular intervals for 36-hour periods. Maximum accuracy of isotope measurement on a single specimen was obtained 8-20 hours after isotope dosing. The Dicopac investigation is a useful simple screening test in the differential diagnosis of patients with a megaloblastic bone marrow and combined low serum B(12) and folate concentrations. When carried out by the standard technique, the degree of discrimination between normal and abnormal ratios is of limited diagnostic significance in one-third of patients.

Topics: Aged; Anemia, Megaloblastic; Anemia, Pernicious; Cobalt Radioisotopes; Diagnosis, Differential; Humans; Intrinsic Factor; Middle Aged; Vitamin B 12

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Autoantibodies; Diagnosis, Differential; FIGLU Test; Gastric Juice; Gastritis; History, 18th Century; History, 19th Century; History, 20th Century; Humans; Intrinsic Factor; Prognosis; Vitamin B 12

Topics: Anemia, Megaloblastic; Anemia, Pernicious; Female; Folic Acid; Hematopoiesis; Humans; Ileum; Intrinsic Factor; Pregnancy; Vitamin B 12; Vitamin B 12 Deficiency

In most cases megaloblastic anaemias are the sequel of a deficiency of vitamin B12, more infrequently of a deficiency of folic acid of different etiology. Oriented to frequency and anamnesis the diagnostics follows the leading symptoms of pernicious anaemia (straw colour, glossitis, achlorhydria) and on the basis of special findings in the peripheral blood (hyperchromacia, megalocytosis, much decreased number of reticulocytes, increased iron and bilirubin level) it leads to the proved suspicion of a megaloblastic anaemia. This suspicion is ascertained by the investigation of the bone-marrow, with the help of aimed investigations the anaemia is further clarified differential-diagnostically. An unclear anaemia should not be treated ex juvantibus with vitamin B12 and/or folic acid. The therapy, always taking into consideration a possible basic disease, is carried out by parenteral application of vitamin B12, possibly in form of hydroxocobalamine or by folic acid. In persisting disturbance of the resorption of vitamin B12 on account of the threatening complication of a funicular spinal disease the long-term therapy must never be interrupted, unless in normal haematological findings.

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Anemia, Pernicious; Diagnosis, Differential; Humans; Intrinsic Factor; Vitamin B 12; Vitamin B 12 Deficiency

Because virtually all cases of vitamin B12 deficiency seen in this country are due to malabsorption, the availability of radioactive vitamin B12 for direct measurement of absorption of this essential nutrient has proved to be of great clinical value. These tests are useful not only in demonstrating vitamin B12 malabsorption but also often in defining the pathophysiological mechanism responsible for this abnormality. The urinary excretion test of Schilling remains the most useful test for vitamin B12 absorption. Minor precautions and modifications in technique make the test results more reliable and easier to interpret. The 8-hr plasma test for vitamin B12 absorption can no longer be considered acceptable. Some patients with vitamin B12 malabsorption have results in the normal range when studied by this method. Serum vitamin B12 assays utilizing radioactive vitamin B12 and the isotope dilution principle are not widely used and are useful screening tests. Low normal or borderline results observed in patients with clinical evidence suggestive of vitamin B12 deficiency should be interpreted with caution or confirmed by radioactive vitamin B12 absorption studies. Radioactive vitamin B12 can also be used for rapid, reliable assay of gastric intrinsic factor, antibody to intrinsic factor and unsaturated vitamin B12 serum. Methods using radioactive folate compounds for similar in vivo and in vitro studies are not yet applicable for routine use in nuclear medicine laboratories.

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Anemia, Pernicious; Cobalt Radioisotopes; Erythrocytes; Folic Acid; Folic Acid Deficiency; Humans; Intestinal Absorption; Intrinsic Factor; Radioimmunoassay; Radioisotope Dilution Technique; Schilling Test; Tritium; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Anemia, Pernicious; Gastrectomy; Humans; Ileum; Intrinsic Factor; Malabsorption Syndromes; Metabolism, Inborn Errors; Schilling Test; Time Factors; Vitamin B 12

Topics: Administration, Oral; Adult; Anemia, Macrocytic; Anemia, Megaloblastic; Female; Humans; Intrinsic Factor; Peutz-Jeghers Syndrome; Tetracycline; Vitamin B 12 Deficiency

Topics: Adolescent; Adult; Agammaglobulinemia; Anemia, Macrocytic; Anemia, Megaloblastic; Antibody Formation; Chronic Disease; Female; Gastric Juice; Humans; Immunoglobulin A; Immunoglobulin G; Immunologic Deficiency Syndromes; Intrinsic Factor; Malabsorption Syndromes; Male; Proteinuria; Syndrome; Vitamin B 12 Deficiency

The blood concentrations of vitamin B12 and folate, which are very useful in diagnosis of megaloblastic anemia and of these factors' dificiencies, are actually measured by precise, rapid, and specific competitive binding radioassays. Futher clinical advantages can be reached with the application of other in vitro radioisotope techniques, such as radioassay of IF, of antibodies anti-IF, of transcobalamins, and of FABP (folic acid binding protein). The major impact of the vitamin B12, folates and other related radioassays has been to permit more Hospitals and laboratories to do these determinations, replacing the more time-consuming, relatively imprecise, and often artifactual microbiological assays.

Topics: Anemia, Megaloblastic; Anemia, Sideroblastic; Antibodies; FIGLU Test; Folic Acid; Folic Acid Deficiency; Intrinsic Factor; Radioimmunoassay; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Adult; Aged; Aged, 80 and over; Anemia, Megaloblastic; Anemia, Pernicious; Antibodies; Arthritis, Rheumatoid; Female; Folic Acid Deficiency; Humans; Intrinsic Factor; Male; Middle Aged; Vitamin B 12 Deficiency

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Anemia, Pernicious; Celiac Disease; Deficiency Diseases; Diagnosis; Female; Folic Acid; Humans; Intrinsic Factor; Malabsorption Syndromes; Physiology; Pregnancy; Pregnancy Complications; Pregnancy Complications, Hematologic; Sprue, Tropical; Vitamin B 12

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Blood Cell Count; Deficiency Diseases; Drug Therapy; Female; Folic Acid; Folic Acid Deficiency; Humans; Intrinsic Factor; Malabsorption Syndromes; Metabolism; Pregnancy; Pregnancy Complications; Pregnancy Complications, Hematologic; Vitamin B 12; Vitamin B 12 Deficiency

Topics: Anemia; Anemia, Macrocytic; Anemia, Megaloblastic; Drug Therapy; Gastrectomy; Humans; Intrinsic Factor; Vitamin B 12

Topics: Anemia; Anemia, Megaloblastic; Gastric Juice; Intrinsic Factor; Vitamin B 12; Vitamin B Complex

Two of the mechanisms for vitamin B(12) deficiency, leading to megaloblastic anemia, are the result of surgically produced abnormalities of the gastrointestinal tract. The basic mechanism is different for each lesion. Total gastrectomy results in complete lack of intrinsic factor which is necessary for vitamin B(12) absorption. It is believed that if patients survive long enough and are not given prophylactic vitamin B(12) therapy, all would develop megaloblastic anemia. Intestinal anastomosis leading to stasis of intestinal contents, with overgrowth of bacteria may cause vitamin B(12) deficiency through bacterial interference with the utilization of vitamin B(12). Use of radioactive vitamin B(12) (cobalt(60)-labeled B(12)) has led to a better understanding of the pathogenesis of both types of megaloblastic anemia. The radioactive vitamin provides a useful tool for study of its absorption from the gastrointestinal tract.

Topics: Anastomosis, Surgical; Anemia; Anemia, Megaloblastic; Antibiosis; Digestive System Abnormalities; Gastrectomy; Gastrointestinal Tract; Hematinics; Humans; Intrinsic Factor; Vitamin B 12; Vitamin B 12 Deficiency; Vitamin B Complex; Vitamins

Topics: Anemia; Anemia, Megaloblastic; Gastric Juice; Hematinics; Intrinsic Factor; Vitamin B 12

Topics: Anemia; Anemia, Megaloblastic; Folic Acid; Gastric Juice; Hematinics; Humans; Intrinsic Factor; Leucovorin; Vitamin B 12

The newer hematinics are merely refinements of preexisting forms of treatment, but they have aided particularly in a better understanding of the deficiency states. The intrinsic factor of Castle has not been isolated from the gastric juice, and the interrelationships of this substance with the extrinsic factor (vitamin B(12)) and folic acid have not been defined at this time. Vitamin B(12) appears to be the active principle of refined liver extract and alone is probably adequate treatment for pernicious anemia. The other varieties of megaloblastic anemia may result from deficiency of vitamin B(12) or folic acid, although generally treatment with the latter brings about complete and lasting remission. The use of multihematinics and multivitamin preparations containing folic acid is to be condemned, particularly because of the possibility of their obscuring anemia and thwarting diagnosis of pernicious anemia until neurologic complications have taken place. Saccharated oxide of iron is a relatively safe preparation for intravenous administration, but the indications for its use are few. Because the body has no mechanism for iron excretion, only the amount of iron necessary to make up a deficiency should be given, although there is no definite evidence that hemochromatosis results from overdosage.

Topics: Anemia; Anemia, Iron-Deficiency; Anemia, Megaloblastic; Anemia, Pernicious; Folic Acid; Hematinics; Humans; Intrinsic Factor; Iron; Iron Compounds; Iron Metabolism Disorders; Liver Extracts; Substance-Related Disorders; Vitamin B 12; Vitamins