A 3-year-old girl developed normally until 14 months of age, after which she lost acquired speech and purposeful hand use. Head circumference growth has decelerated off her previous curve. She now shows continuous stereotypic hand-wringing movements and an apraxic gait. Which gene is implicated?
- A MECP2 ✓
- B FMR1
- C UBE3A
- D CDKL5
Correct answer: A. MECP2
Explanation
This is Rett syndrome, an X-linked dominant disorder caused by MECP2 mutations, affecting almost exclusively girls because the mutation is usually lethal in males. The classic course is normal development for 6 to 18 months followed by regression, acquired microcephaly, loss of purposeful hand skills replaced by midline hand-wringing stereotypes, and gait apraxia. Angelman syndrome (UBE3C) differs by its happy demeanor and laughter, and CDKL5 defines an earlier-onset epileptic variant.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.