Which autosomal recessive disorder results from accumulation of a lipid that damages the nervous system in infancy?

• A. Tay-Sachs disease
• B. Phenylketonuria (PKU)
• C. Achondroplasia
• D. Fragile X syndrome

Answer: (A)

Lipid buildup in neurons due to a lysosomal storage defect is the hallmark. Tay-Sachs disease results from a deficiency of the enzyme hexosaminidase A, causing GM2 ganglioside to accumulate in neuronal lysosomes and lead to progressive neurodegeneration in infancy. This pattern fits autosomal recessive inheritance, where two defective copies are needed. By contrast, PKU is also autosomal recessive but involves accumulation of phenylalanine, not a lipid, and causes broad developmental issues without the characteristic lipid-driven neurodegeneration. Achondroplasia is a skeletal disorder from FGFR3 mutation, not related to lipid storage in the nervous system, and Fragile X is X-linked with CGG repeats affecting neural development rather than lipid accumulation.