This disease has a remarkably variable phenotype. It can present at or before birth or at up to 2 years as an acute form with hepatosplenomegaly and jaundice. Some of these patients die but others survive with progressive neurological degeneration. Alternatively it may appear as a sub-acute form from infancy to 18 years of age with progressive psychomotor retardation, hepatosplenomegaly, foam cells and sea-blue histiocytosis. Most of these patients have a vertical supranuclear ophthalmoplegia. Finally there is a chronic form presenting in adulthood with a variable and still incompletely defined phenotype.