Hypothyroidism with subacute pseudomyotonia--an early form of Hoffmann's syndrome? Report of a case.

A 25-year-old man was admitted to the hospital because of painful muscle cramps and action myospams of subacute onset and 6 weeks' duration. No myotonia could be demonstrated objectively and his deep tendon reflexes showed no prolongation of the relaxation phase. Serum creatinine was raised but creatinine clearance was normal. Serum levels of aldose, CPK, ASAT and ALAT were increased but ordinary light microscopy revealed no histological signs of muscle disease in a quadriceps biopsy. ECG showed a prolonged PQ interval and flat T waves in the left precordial leads. Laboratory tests of thyroid function revealed intensive hypothyroidism, and high titers of circulating thyroid antibodies were demonstrated. During 2 1/2 months of thyroid therapy, the muscle symptoms gradually disappeared completely and the patient could return to work. By that time the serum enzymes and the ECG had normalized. Despite the lack of objective signs of myotonia, we consider that the very dominant subjective muscle symptoms, severe enough to prevent the patient from performing his ordinary manual work and completely reversible on thyroid therapy, justify the designation of hypothyroid myopathy. The question is raised whether the case represents an early form of Hoffmann's syndrome.