methimazole and Lymphatic-Diseases

A 12-year-old neutered male domestic shorthair cat presented for chronic, localized, swelling and crusting of the left upper lip, weight loss, sporadic vomiting, and focal alopecia between the scapulae was diagnosed with hyperthyroidism and regional eosinophilic lymphadenitis. Treatment with methimazole exacerbated an underlying hypersensitivity disorder leading to marked generalized lymphadenopathy that histologically mimicked lymphoma.

Topics: Animals; Cat Diseases; Cats; Hyperthyroidism; Lymphatic Diseases; Male; Methimazole; Pruritus

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Hyperthyroidism; Lymphatic Diseases; Methimazole

Topics: Animals; Antithyroid Agents; Carbimazole; Cat Diseases; Cats; Diagnosis, Differential; Hyperthyroidism; Lymphatic Diseases; Methimazole

A nine-year-old, domestic shorthair cat was diagnosed with hyperthyroidism and treated with methimazole, which resulted in lethargy, inappetence and marked generalised lymphadenomegaly within two weeks of initiation of therapy. Cytology, histopathology and immunohistochemistry were suggestive of atypical lymphoid hyperplasia. Cessation of treatment resulted in resolution of all clinical signs and physical abnormalities within two days. Subsequent treatment with radioactive iodine cured this cat of its hyperthyroidism. The lymphadenomegaly did not return at any stage and the cat is currently asymptomatic. Although methimazole administration for feline hyperthyroidism has been associated with many side effects, lymphadenomegaly has, to the authors' knowledge, not been previously reported.

Topics: Animals; Antithyroid Agents; Cat Diseases; Cats; Diagnosis, Differential; Hyperthyroidism; Lymphatic Diseases; Male; Methimazole