Niemann-Pick disease type A is caused by sphingomyelinase deficiency, leading to sphingomyelin accumulation. The cell type primarily engorged with lipid is:

• A Hepatocytes (hepatomegaly due to lipid storage)
• B Neurons (neurodegeneration due to GM1 ganglioside accumulation)
• C Renal tubular cells (renal failure predominates)
• D Macrophages/monocytes (foam cells in liver, spleen, and bone marrow) ✓

Explanation

Sphingomyelinase is most active in macrophages/monocytes responsible for membrane turnover via phagocytosis; in Niemann-Pick disease, these cells become engorged with sphingomyelin, forming foam cells seen in the liver, spleen, lungs, and bone marrow (causing hepatosplenomegaly and pancytopaenia). Type A also involves neurodegeneration due to neuronal sphingomyelin accumulation and cherry-red spot. GM1 ganglioside accumulation is Tay-Sachs/Sandhoff mechanism.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

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Written and medically reviewed by the StethoPrep medical team.