USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

What is the characteristic feature of Hand-Foot-Genital Syndrome?

1. Central limb defects

2. Malformed digits

3. Kidney malformation

4. Hypoplastic fourth digit

The correct answer is: Malformed digits

Hand-Foot-Genital Syndrome is primarily associated with specific developmental abnormalities, particularly affecting the limbs and genitals. A hallmark feature of this condition is the presence of malformed digits, which includes various deformities of the fingers and toes. These anomalies can vary in severity and type, often presenting as syndactyly (fused fingers or toes) or other disorganized digit structures. The condition itself arises due to mutations in the HOXD13 gene, which plays a critical role in the development of limbs and genitalia. As a result, individuals with Hand-Foot-Genital Syndrome often exhibit significant variations in limb formation and digit morphology, thus making malformed digits the defining feature of the syndrome. In contrast, central limb defects, kidney malformations, or a hypoplastic fourth digit might occur in other congenital syndromes, but they are not characteristic of Hand-Foot-Genital Syndrome. The focus on digit malformations underscores the specific implications of the genetic mutations involved and their impact on normal limb development.