Sea blue histiocytosis in a patient with chronic non-neuropathic Niemann-Pick disease.

A patient with Niemann-Pick disease is reported together with family studies. Her liver and bone marrow were shown to be infiltrated with sea blue histiocytes. Other organs, spleen and lung, were presumably also involved but histological proof was not obtained. Enzyme assay of leucocytes, lymphocytes, and cultured skin fibroblasts showed the patient to be deficient in sphingomyelinase activity. In fibroblasts, activity was 5% of normal while for the parents activity was about 50% of normal. The expected partial deficiency was not found using leucocytes or lymphocytes from the parents. Heat stability studies on fresh fibroblast extracts from the propositus indicated that residual sphingomyelinase activity was slightly more labile than that of the controls. It seems clear that chronic Niemann-Pick disease without neurological involvement is associated with sea blue histiocytosis.