A 46,XY newborn has markedly bowed femora and humeri, hypoplastic scapulae, and external genitalia resembling those of a normal female. Sequencing most likely reveals a mutation affecting which gene?

• A DAX1
• B WT1
• C SF1
• D SOX9 ✓

Explanation

Campomelic dysplasia arises from SOX9 loss-of-function or from regulatory mutations that abolish SOX9 expression near the gene. SOX9 drives chondrogenesis and, downstream of SRY, directs differentiation of the testes, so affected 46,XY individuals show bowed long bones and XY gonadal dysgenesis. WT1 and SF1 act upstream at earlier stages of gonad ridge formation and are not linked to campomelic skeletal findings.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.