ONSET OF HYPOTHYROIDISM WITH POLYMYOSITIS-LIKE CLINICAL-FEATURES IN ELDERLY PATIENTS

Impaired muscle function may be a predominant aspect of hypothyroidism and is virtually present in all patients with overt thyroid failure. Less common is the onset of hypothyroidism with clinical features mimi cking a polymyositis. We have observed 3 patients, whose age ranged 63 -68 years, presenting with muscle aches, cramps, proximal weakness and stiffness. Two patients had dysphagia. Serum creatine kinase (CK) and electromyography (EMG) were altered in two patients. Muscle biopsy sh owed type II atrophy, sporadic type I and type II grouping, ''core-lik e'' areas, and some myopathic changes such as central nuclei and muscl e necrosis. No inflammatory changes were present. Immunohistochemistry of several muscle cytoskeletal proteins revealed increased desmin in ''core-like'' areas. Detection of serum thyroid hormone levels reveale d very low triiodo-L-thyronine (T3) and thyroxine (T4), whereas thyroi d-stimulating hormone (TSH) was greatly increased as well as serum ant i-thyroglobulin, anti-peroxidase and anti-microsome antibodies. The pa tients were diagnosed having a hypothyroid myopathy due to Hashimoto t hyroiditis. L-thyroxine treatment normalized clinical and hormone leve ls, but serum antibodies remained elevated. Muscle biopsy was fundamen tal to establish the correct diagnosis in our patients. Presence of ov erexpression of desmin in cores, as described in target lesions in neu rogenic diseases, may suggest a nerve-mediated pathogenesis of hypothy roid myopathy.