A 6-month-old girl has failure to thrive, developmental regression, a cherry-red spot on fundoscopy, exaggerated startle response (hyperacusis), and hypotonia. The parents are of Ashkenazi Jewish origin. Enzyme assay reveals deficient hexosaminidase A with NORMAL hexosaminidase B. What is the inheritance pattern of this condition?

• A X-linked recessive
• B Autosomal dominant
• C Mitochondrial inheritance
• D Autosomal recessive ✓

Explanation

Tay-Sachs disease (HEXA gene mutation, deficient hexosaminidase A, normal hexosaminidase B) is inherited in an autosomal recessive pattern. It is particularly prevalent in Ashkenazi Jewish populations (~1 in 30 carrier frequency vs ~1 in 300 in general population). The classical infantile form presents at 4–6 months with developmental regression, exaggerated startle to sound (hyperacusis), cherry-red spot, and motor decline. There is no hepatosplenomegaly (unlike Sandhoff). It is fatal by 3–4 years, with no curative treatment currently available.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.