gq1b-ganglioside and Myasthenia-Gravis

Autoantibodies to acetylcholine receptors and to voltage-gated calcium and potassium channels are thought to be pathogenic in three peripheral neurological disorders: myasthenia gravis, the Lambert Eaton syndrome and acquired neuromyotonia. However, evidence for the role of antibodies in conditions involving the central nervous system, is scanty or unclear. This review describes the ways in which the roles of autoantibodies have been defined in the peripheral diseases, and discusses the more controversial evidence for involvement of autoantibodies in some central disorders such as multiple sclerosis.

Topics: Autoantibodies; Calcium Channels; Cell Line; Gangliosides; Humans; Isaacs Syndrome; Lambert-Eaton Myasthenic Syndrome; Myasthenia Gravis; Nervous System Diseases; Neurons; Receptors, Cholinergic

This review primarily concerns two issues. First, in myasthenia gravis, what mechanisms are likely to underlie the low threshold for extraocular muscle involvement in this disease? Second, what is the likely importance of anti-GQ1b ganglioside antibodies in the diagnosis and causation of Miller-Fisher syndrome?

Topics: Autoantibodies; Diagnosis, Differential; Gangliosides; Humans; Myasthenia Gravis; Oculomotor Muscles; Ophthalmoplegia; Polyradiculoneuropathy; Receptors, Cholinergic; Reflex, Abnormal

A 69-year-old woman presented with acute bilateral ptosis, ophthalmoplegia, ataxia, and hyporeflexia in the extremities following an antecedent upper respiratory infection. We suspected that she had Miller Fisher syndrome (MFS) and performed an edrophonium test (ET) to rule out myasthenia gravis (MG). Edrophonium chloride improved the patient's bilateral ptosis, but not her ophthalmoplegia. Given the absence of the waning phenomenon on electrophysiological examination, the anti-acetylcholine receptor antibody, and a diurnal variation of symptoms, we concluded that the ET result was a false-positive. A diagnosis of MFS was confirmed by the presence of a positive anti-GQ1b antibody. To our knowledge, this is the first case report of MFS with a false-positive ET.

Topics: Aged; Autoantibodies; Biomarkers; Diagnosis, Differential; Edrophonium; False Positive Reactions; Female; Gangliosides; Humans; Miller Fisher Syndrome; Myasthenia Gravis

Intravenous immunoglobulin (IVIg) is an effective treatment in chronic inflammatory demyelinating polyneuropathy (CIDP). In most patients, the optimal IVIg dose and regime is unknown. Polyvalent immunoglobulin (Ig) G form idiotypic/anti-idiotypic antibody pairs in serum and IVIg preparations. We determined IgG dimer levels before and after IVIg treatment in CIDP patients with the aim to explore their utility to serve as a surrogate marker for treatment response.. IgG was purified from serum of five controls without treatment, as well as from serum of 16 CIDP patients, two patients with Miller Fisher syndrome (MFS), and one patient with myasthenia gravis before and after treatment with IVIg. IgG dimer levels were determined by size exclusion chromatography. IgG dimer formation was correlated with clinical response to IVIg treatment in CIDP. Re-monomerized IgG dimer fractions were analyzed for immunoreactivity against peripheral nerve tissue.. IgG dimer levels were significantly higher in post- compared to pre-IVIg infusion samples. Low post-treatment IgG dimer levels in CIDP patients were associated with clinical worsening during IVIg treatment. Re-monomerized IgG dimer fractions from CIDP patients showed immunoreactivity against peripheral nerve tissue, whereas similarly treated samples from MFS patients showed immunoreactivity against GQ1b.. Assessment of IgG dimer levels could be a novel approach to monitor CIDP patients during IVIg treatment, but further studies in larger cohorts are warranted to explore their utility to serve as a potential therapeutic biomarker for IVIg treatment response in CIDP.

Topics: Aged; Biomarkers; Dimerization; Female; Gangliosides; Humans; Immunoglobulin G; Immunoglobulins, Intravenous; Male; Middle Aged; Miller Fisher Syndrome; Myasthenia Gravis; Nerve Fibers; Peripheral Nerves; Polyradiculoneuropathy, Chronic Inflammatory Demyelinating

PURPOSE.: Miller Fisher syndrome (MFS) is a rare immune-mediated neuropathy that commonly presents with diplopia after the acute onset of complete bilateral external ophthalmoplegia. Ophthalmoplegia is often accompanied by other neurological deficits such as ataxia and areflexia that characterize MFS. Although MFS is a clinical diagnosis, serological confirmation is possible by identifying the anti-GQ1b antibody found in most of the affected patients. We report a patient with MFS who presented with clinical signs suggestive of ocular myasthenia gravis but in whom the correct diagnosis was made on the basis of serological testing for the anti-GQ1b antibody. CASE REPORT.: An 81-year-old white man presented with an acute onset of diplopia after a mild gastrointestinal illness. Clinical examination revealed complete bilateral external ophthalmoplegia and left-sided ptosis. He developed more marked bilateral ptosis, left greater than right, with prolonged attempted upgaze. He was also noted to have a Cogan lid twitch. Same day evaluation by a neuro-ophthalmologist revealed mild left-sided facial and bilateral orbicularis oculi weakness. He had no limb ataxia but exhibited a slightly wide-based gait with difficulty walking heel-to-toe. A provisional diagnosis of ocular myasthenia gravis was made, and anticholinesterase inhibitor therapy was initiated. However, his symptoms did not improve, and serological testing was positive for the anti-GQ1b immunoglobulin G antibody, supporting a diagnosis of MFS. CONCLUSIONS.: Although the predominant ophthalmic feature of MFS is complete bilateral external ophthalmoplegia, it should be recognized that MFS has variable associations with lid and pupillary dysfunction. Such confounding neuro-ophthalmic features require a thorough history, neurological examination, neuroimaging, and serological testing for the anti-GQ1b antibody to arrive at a diagnosis of MFS.

Topics: Aged, 80 and over; Antibodies; Diagnosis, Differential; Diplopia; Eye Movements; Gangliosides; Humans; Magnetic Resonance Imaging; Male; Miller Fisher Syndrome; Myasthenia Gravis

The co-occurrence of myasthenia gravis (MG) and Guillain Barré syndrome (GBS) is uncommon with a few reported cases in the literature. There is only one reported case of MG and Miller Fisher variant of GBS. We described an 84 year old Chinese woman with underlying seropositive myasthenia gravis (MG) who presented with ophthalmoplegia, areflexia and acute neuromuscular weakness. She was proved to have co-occurrence of MG and GBS/Miller Fisher overlap syndrome with positive anti-GQ1b antibody. The unusual finding in this patient raises an interesting question on their pathogenesis with the possibility that prior activation of the immune system may predispose the development of autoantibodies against other antigens within the same set of muscles.

Topics: Aged, 80 and over; Antibodies; Female; Gangliosides; Guillain-Barre Syndrome; Humans; Myasthenia Gravis; Serologic Tests

We describe the case of a male patient with ocular myasthenia gravis who developed a diabetic neuropathy similar to chronic inflammatory demyelinating polyradiculoneuropathy associated with transient generalized 'myokymic' discharges and distal weakness. He had antibodies against acetylcholine receptor and GQ1b ganglioside, but not anti-voltage-gated K(+) channel antibodies. Serial electrophysiological and immunological findings showed that diabetes was involved in the immune-mediated mechanism of peripheral neuropathy. We hypothesize that the concomitant appearance of distal motor weakness and decreased compound muscle action potentials upon repetitive nerve stimulation, together with increased distal motor latency and generalized peripheral nerve hyperexcitability, were all related to transient serum positivity to anti-GQ1b antibodies.

Topics: Aged; Diabetes Mellitus, Type 2; Diabetic Neuropathies; Electrophysiology; Gangliosides; Humans; Immunoglobulin G; Immunoglobulin M; Male; Myasthenia Gravis