This disease is classified into three main types. Type 1 (non-neuronopathic, chronic or adult type) is highly variable in severity, progression and age of onset, which has been reported in the first year and late adult life. Features include splenomegaly, pancytopaenia due to hypersplenism, hepatomegaly and skeletal involvement which may cause mild to severe bone pain, usually in the long bones, and occasionally also pathological fractures. Radiologically there is often aseptic necrosis of the femoral heads, and erosion of the long bones. Pulmonary hypertension and a yellowish-coloured skin occurs in some affected adults. Neurological involvement is typically absent but has been reported in a few cases. Type 2 (acute neuronopathic or infantile type) is a rapidly progressive neurovisceral disease with onset at about six months, severe hepatosplenomegaly and early death before two years. Type 3 (sub-acute neuronopathic or juvenile type) is less rapidly progressive and is characterised by ataxia, myoclonus, seizures and hepatosplenomegaly.
ENZYME TESTS: Deficiency of lysosomal a-glucosidase (glucocerebrosidase) activity is the primary defect. Assay of chitotriosidase is used as an additional test.