Nephropathic cystinosis is an autosomal recessive lysosomal disease in which cystine cannot exit the lysosome to complete its degradation in the cytoplasm, thus accumulating in tissues. Some patients develop a distal myopathy involving mainly hand muscles. Myopathology descriptions from only 5 patients are available in the literature. Here, the authors present a comprehensive clinical, pathological and genetic description of 3 patients from 2 families with nephropathic cystinosis. Novel pathological findings consisting in sarcoplasmic deposits reactive for slow myosin were identified. Three previously known and one novel mutation are reported. The authors propose that nephropathic cystinosis should be included in the differential diagnosis of distal myopathies in those with early renal failure.
