Adult Niemann-Pick disease with sea-blue histiocytes in the spleen.

Two cases of adult chronic non-neuronopathic Niemann-Pick disease (type B) are reported. In both, unexplained splenomegaly was present, and one had signs of splenic rupture. In both cases, histologic examination revealed collections of foamy histiocytes in the spleen, which stained sea-blue with Giemsa and gave the histochemical reactions of ceroid. Ultrastructurally, the histiocytes were filled with lysosomes containing myelin figures, some of which had the characteristic fingerprint pattern. The diagnosis was confirmed biochemically by measurements of tissue sphingomyelin and liver lysosomal sphingomyelinase. In adult Niemann-Pick disease, both the characteristic staining reactions and the elevation of tissue sphingomyelin may be demonstrated in formalin-fixed material. Enzyme studies, however, require fresh leukocytes or biopsy tissue.