Symptoms are related to the organs in which sphingomyelin accumulates. Enlargement of the liver and spleen (hepatosplenomegaly) may cause reduced appetite, abdominal distension, and pain. Enlargement of the spleen (splenomegaly) may also cause low levels of platelets in the blood (thrombocytopenia). Accumulation of sphingomyelin in the central nervous system (including the cerebellum) results in unsteady gait (ataxia), slurring of speech (dysarthria), and difficulty swallowing (dysphagia). Basal ganglia dysfunction causes abnormal posturing of the limbs, trunk, and face (dystonia). Upper brainstem disease results in impaired voluntary rapid eye movements (supranuclear gaze palsy). More widespread disease involving the cerebral cortex and subcortical structures causes gradual loss of intellectual abilities, causing dementia and seizures. Bones also may be affected, with the disease causing enlarged bone marrow cavities, thinned cortical bone, or a distortion of the hip bone called coxa vara. Sleep-related disorders also occur with the condition, such as sleep inversion, sleepiness during the day and wakefulness at night. Gelastic cataplexy, the sudden loss of muscle tone when the affected patient laughs, is also seen.
Niemann–Pick disease
Wilson's disease
Wilson–Mikity syndrome
Haemochromatosis type 3
Mowat–Wilson syndrome
Hemochromatosis type 4
Gaucher's disease
Maroteaux–Lamy syndrome