A histochemical study of
lipids in bone marrow smears was performed in a series of 15 cases of
Niemann-Pick disease (
NPD). It revealed significant differences in the amount of
lipids stored in macrophages of
sphingomyelinase (SMase) deficiency (types A, B) and type C. Early deposition of uniform, anisotropic droplets of
sphingomyelin (Maltese-cross birefringence) in lysosomes was a feature of a 9-member group of SMase deficiency (types A, B). The type C group (six cases) was characterized by a remarkable difference in the degree of
phospholipid, mainly
sphingomyelin, deposition. The total amount of
phospholipids was small on average, and very often inversely proportional to pronounced structural storage changes. This indirect relationship was most prominent in the early phase of the disease and grew less prominent as the disease progressed further. The stored
lipid was primarily isotropic. In longer lasting cases of both categories (SMase deficiency and type C) a considerable part of the storage cell population displayed
ceroid deposition giving the appearance of a 'sea-blue histiocyte' independent of the type of
NPD, but with definite predominance in SMase deficiency. The diagnostic value of the findings is discussed, and some pathogenetic conclusions suggested, particularly as regards type C.
Lipid histochemistry of bone marrow smears is highly recommended as it represents a simple but highly efficient approach, capable of yielding valuable diagnostic information.