Ultrastructure of the liver in a case of childhood cystinosis.

Ultrastructural findings in the liver in a case of childhood cystinosis are reported. Crystalline structures were found mainly in Kupffer cells. The presence of dark cells, with or without crystals, was the most striking feature observed. Such cells have already been noted within the kidney on one occasion when it was shown that the dark substance was L-cystine (Spear et al., 1971). In this case identical dark material was also found extracellularly. The data shows that free cystine can fill cell cytoplasm and extracellular spaces and the possibility that cystine overproduction may take place in the hyaloplasm should be considered. Extracellular location of cystine in the tubules might account for an increase in epithelial permeability and thus for the Fanconi syndrome.