Transitory type of sphingomyelinase deficient Niemann-Pick disease: clinical and morphological studies and follow-up of two sisters.

The transitory type is a rare and ill-defined variant of sphingomyelinase deficient NPD. Here reported are full clinical and morphological studies on two sisters with the transitory type. Our cases have the following features in common: 1) prominent visceral involvement from early infancy, such as marked hepatosplenomegaly, pulmonary infiltration, and numerous characteristic foam cells in the bone marrow aspirates; 2) very low sphingomyelinase activities in cultured skin fibroblasts; 3) atypical cherry-red spots in the retina; despite 4) absence of any neurological symptoms even at the age of 5 years and 6 months, and 3 years and 9 months, respectively. Furthermore, a few lines of evidence indicating nervous system involvement are also disclosed, that is, 5) vacuolated macrophages in the cerebrospinal fluid and ultrastructurally typical inclusion bodies in axons and Schwann cells in the rectal biopsy specimens, which were firstly revealed in this type of NPD. It is stressed that every case with apparent type B NPD should be searched for the presence or absence of neuronal involvement by not merely fundoscopy but other available means as we employed, which would greatly contribute to elucidate the clinico-pathogenetical knowledge not to mention the current classification of NPD.