A 6-month-old infant presents with progressive loss of previously attained motor milestones, an exaggerated startle response to sound (hyperekplexia), a cherry-red spot on fundoscopy, and progressive macrocephaly. Enzyme assay shows absent hexosaminidase A. The diagnosis is:

• A Niemann-Pick disease type A
• B Tay-Sachs disease ✓
• C Gaucher disease type 2
• D Krabbe disease

Explanation

Tay-Sachs disease is an autosomal recessive lysosomal storage disorder caused by deficiency of hexosaminidase A (HEXA), leading to accumulation of GM2 ganglioside in neurons. The classic infantile form presents at 3–6 months with progressive neurodegeneration, hyperekplexia (exaggerated acoustic startle), macrocephaly, cherry-red spot at the fovea, and no hepatosplenomegaly (distinguishing it from Niemann-Pick type A which also has a cherry-red spot but with hepatosplenomegaly). Gaucher type 2 has hepatosplenomegaly and neurological features but no cherry-red spot. Krabbe disease causes early infantile neurodegeneration with increased CSF protein and elevated galactosylceramidase deficiency.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.