A 15-month-old infant presents with progressive psychomotor regression, exaggerated startle response (hyperekplexia), cherry-red spot on fundal examination, and hypotonia progressing to hypertonia. Lysosomal enzyme assay shows absence of hexosaminidase A activity. The diagnosis is:
- A Niemann-Pick disease type A
- B Tay-Sachs disease (GM2 gangliosidosis) ✓
- C Gaucher disease type 2
- D Krabbe disease (globoid cell leukodystrophy)
Correct answer: B. Tay-Sachs disease (GM2 gangliosidosis)
Explanation
Tay-Sachs disease is caused by deficiency of hexosaminidase A (HEXA), leading to GM2 ganglioside accumulation in neurons. Classic infantile form presents at 3–6 months with progressive neurodegeneration, exaggerated startle (hyperekplexia), cherry-red spot (ganglion cell accumulation around the fovea), macrocephaly, and death by 3–4 years. Niemann-Pick type A also has a cherry-red spot but shows sphingomyelinase deficiency with hepatosplenomegaly. Gaucher type 2 has visceral involvement and oculomotor problems.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.