[Coexistence of hypothyroidism with polymyositis or dermatomyositis]

Muscle weakness with elevation of muscle enzymes may be a predominant manifestation of many diseases, among them myositis and hypothyroidism.

Between 1997 and 2005, polymyositis (PM) or dermatomyositis (DM) was diagnosed in 28 patients (7 males, 21 females) referred to our Department of Rheumatology. Coexistence of hypothyroidism and poly/dermatomyositis was established in seven patients (25%), all of them women. Five of them fulfilled the diagnostic criteria for PM, two for DM. The mean age at the time of diagnosis was 46.1 years (40-54 years). Four patients were diagnosed with chronic autoimmune thyroiditis, in two patients the autoimmune etiology was probable, whereas one patient was diagnosed with hypothyroidism secondary to strumectomy for follicular adenoma. We present and compare signs and symptoms characteristic for hypothyroidism and poly/dermatomyositis. Hypothyroidism may be masked by symptoms of poly/ dermatomyositis especially when the course of myositis is rapid.

Every patient suspected of poly/dermatomyositis should be tested for thyroid hormone levels to exclude hypothyroidism with muscle weakness arising from the polymyositis-like syndrome or alternatively to confirm the coexistence of hypothyroidism and poly/dermatomyositis.