Myopathy in two siblings with nephropathic cystinosis

Nephropathic cystinosis is a hereditary disorder characterized by a specific defect in the transport of cystine across the lysosomal membrane leading to an accumulation of protein-free cystine in tissues including conjuctiva liver bone marrow and kidney. Renal transplantation is necessary because of renal failure. With improved life-expectancy neurological complications have been reported including cases of distal myopathy diagnosed ante-and post mortem. We report on two further rare cases of two siblings suffering from cystinosis who developed a predominantly distal myopathy proven electrophysiologically and on biopsy during life. The reported clinical picture of a distal atrophy resembling a neurogenic disease confirms a picture apparently typical in cystinosis. Possible effects of cysteamine therapy on the course of the myopathy are discussed.