After puberty, which feature is characteristic of Fragile X syndrome?

After puberty, which feature is characteristic of Fragile X syndrome?

• A. Small testes
• B. Prominent jaw and macro-orchidism
• C. Normal facial features
• D. Hypothyroidism

Answer: (B)

Fragile X syndrome in males shows a distinctive postpubertal phenotype: enlarged testes (macroorchidism) along with facial features such as a prominent jaw. After puberty, the testicular enlargement becomes a hallmark, and when paired with a prominent jaw, it forms the classic picture of the condition. This results from the CGG repeat expansion in the FMR1 gene leading to reduced FMRP, which underlies the syndrome’s features. Other options don’t fit: small testes would be inconsistent with macroorchidism; normal facial features aren’t typical of Fragile X; and hypothyroidism isn’t a characteristic feature of Fragile X.

Fragile X syndrome in males shows a distinctive postpubertal phenotype: enlarged testes (macroorchidism) along with facial features such as a prominent jaw. After puberty, the testicular enlargement becomes a hallmark, and when paired with a prominent jaw, it forms the classic picture of the condition. This results from the CGG repeat expansion in the FMR1 gene leading to reduced FMRP, which underlies the syndrome’s features.

Other options don’t fit: small testes would be inconsistent with macroorchidism; normal facial features aren’t typical of Fragile X; and hypothyroidism isn’t a characteristic feature of Fragile X.