[Thyrotoxic myopathy].

A variety of neuromuscular disorders has been described in adults in association with overactivity of the thyroid (Millikan and Haines, 1953; Ramsay, 1966; Engel, 1972). The most common of these disorders is a chronic myopathy, characterized by muscular atrophy and weakness involving predominantly proximal muscles (Adams and Rosman, 1971). The myopathic symptoms may precede the symptoms of thyrotoxicosis by many months, and the atrophy and weakness may be so pronounced that it suggests a diagnosis of progressive muscular atrophy or a limb-girdle type muscular dystrophy. Less commonly, myasthenia gravis and periodic paralysis may be associated with thyrotoxicosis. The chronic myopathy and periodic paralysis are always improved by establishing a euthyroid state, suggesting that thyroid dysfunction induces the neuromuscular disorder. The myasthenia gravis, however, is not cured by controlling the thyroid dysfunction and any departure from the euthyroid state increases the severity of the myasthenia (Engel, 1972). Chronic thyrotoxic myopathy has hitherto been reported exclusively in adults. The purpose of this paper is to report that a similar disorder can be associated with thyrotoxicosis in childhood.