Cystinosis of bone.

The authors describe a case of cystinosis of bone that presented initial difficulties in diagnosis. They discuss the clinical features and the radiographic appearances, which demonstrated numerous zones of osteoporosis with a markedly monomelic distribution in the left leg. The condition arose as a result of trauma. Numerous accumulations of intracellular cystine crystals were revealed by the ultramicroscopic study of bone fragments obtained by biopsy, and this led the authors to diagnose the case as cystine thesaurismosis of bone. The case is of interest not only because of its exceptional rarity (it is, perhaps, the first reported case of cystinosis localized exclusively in bone), but also because it was only possible to arrive at a diagnosis by means of ultramicroscopic investigation.