Steroid myopathy complicating McArdle's disease.

McArdle (1951) first described a syndrome characterized by muscle cramps and stiffness after exercise and suggested that this may have been due to defective breakdown of glycogen in skeletal muscle. Deficiency of musclephosphorylase was subsequently demonstrated in two patients with the same syndrome (Schmid and Mahler, 1959; Mommaerts, Illingworth, Pearson, Guillory, and Seraydarian, 1959). Patients with this condition usually first develop symptoms in childhood or adolescence but onset in adult life has also been reported (Engel, Eyerman, and Williams, 1963). Muscle phosphorylase deficiency is believed to be an inherited disorder and several sibships have now been described. The condition appears to be inherited as an autosomal recessive trait (Pearson, 1968) although there is a predominance of males in some reported cases (Hsia, 1968). The occurrence of a proximal myopathy in patients receiving long-term corticosteroid therapy is also well documented (Perkoff, Silber, Tyler, Cartwright, and Wintrobe, 1959; Golding, Murray, Pearce, and Thompson, 1961; Braun, Coste, Delbarre, and Aurel, 1965; Afifi, Bergman, and Harvey, 1968) and a comparable condition has been produced in the experimental animal (D'Agostino and Chiga, 1966; Ritter, 1967; Tice and Engel, 1967; Afifi and Bergman, 1969). In this paper we describe a patient with proven muscle phosphorylase deficiency in whom the course of the disease was modified by prolonged corticosteroid therapy. Electron microscopic examination of biopsy material from this patient revealed ultrastructural abnormalities reminiscent of those described in steroid-induced myopathy in man and in the experimental animal.