A 2 year old retarded child is evaluated by a metabolic specialist. The child's history is significant for failure to thrive and progressive neurologic deterioration, including deafness and blindness. Physical examination is remarkable for hepatosplenomegaly, as well as a cherry-red spot on funduscopic examination. These symptoms are consistent with a diagnosis of?

Hepatosplenomegaly accompanied by progressive neurologic deterioration should make you think of lipid storage diseases; Niemann-Pick disease is the only lipid storage disease in the answer choices. Niemann-Pick disease is due to a deficiency of sphingomyelinase, leading to an accumulation of sphingomyelin. It is most common among Ashkenazic Jews and generally results in death by age 2. The cherry-red spot is also a characteristic of Tay-Sachs disease, but hepatosplenomegaly suggests Niemann-Pick disease rather than Tay-Sachs. Hunter syndrome is a mucopolysaccharidosis, inherited in an X-linked recessive fashion. Pompe's disease is a glycogen storage disease characterized by hypotonia and cardiorespiratory failure. Tyrosinosis is a rare abnormality of tyrosine metabolism that would not produce the listed symptoms. Ref: Ropper A.H., Samuels M.A. (2009). Chapter 37. Inherited Metabolic Diseases of the Nervous System. In A.H. Ropper, M.A. Samuels (Eds), Adams and Victor's Principles of Neurology, 9e.