We report two new cases, in the same family, of type B Niemann-Pick disease associated with sea-blue histiocytes syndrome. In one patient the disease was revealed by spontaneous rupture of the spleen. The sea-blue histiocytes syndrome is due to the histiocytes being overloaded by ceroids, and it usually occurs in a context of blood disease or thesaurismosis. Twenty-five cases of sea-blue histiocytes syndrome associated with type B Niemann-Pick disease have been reported, with rupture of the spleen in two of them. The link between the two conditions is the transformation into ceroids of the sphyngomyelin accumulated in histiocytes.