• Definition: X-linked disorder with progressive loss of intelligence and cognitive abilities such as language, locomotion, and fine motor skills

Mnemonic

Rett for Regress

• Etiology: X-linked dominant gene mutation in methyl-CpG binding protein 2 gene (MECP2 gene)
  • Usually not an inherited gene defect, but rather a sporadic mutation
  • Mutation usually occurs in the paternal allele; thus, females are almost exclusively affected
  • If affected, male fetuses die in utero or shortly after birth.
• Clinical features
  • Normal development until the first symptoms appear, which typically happens at 6–18 months of age
  • Symptoms of neurodevelopmental regression, including:
    • Loss of motor skills, especially targeted hand movements (affected children show characteristic hand wringing)
    • Truncal ataxia, apraxia, choreatic movements
    • Intellectual and verbal disability
    • Seizures
    • Growth failure
    • Scoliosis