Chromosome: Xq28
Gene: MECP2 (methyl-CpG binding protein 2)
Inheritance: X-linked
Clinical features:
(1) almost all affected patients are males (rarely occurs in carrier females with a concomitant abnormality of the X chromosome)
(2) normal body measurements at birth
(3) hypotonia during infancy resulting in feeding difficulties and drooling
(4) mild facial dysmorphic features:
(4a) midfacial hypoplasia
(4b) flat nasal bridge
(4c) large ears
(4d) brachycephaly
(5) developmental delays occur in sitting, crawling and walking
(6) variable gait ataxia
(7) delayed or absent speech
(8) mental retardation, which may be severe
(9) spasticity appears during childhood and is progressive, primarily affecting the lower limbs
(9a) variable joint contractures
(9b) progression to paraplegia requires use of a wheelchair
(10) variable seizures
(11) recurrent infections, especially pneumonia
(12) variable constipation
(13) variable autism spectrum disorder
(14) hypoplasia of the corpus callosum on brain imaging studies
Cytogenetic analysis can detect large duplications, but these are seen in only 5% of patients. Duplication testing using a molecular method (quantitative PCR, multiplex ligation-dependent probe amplification, etc) is required to identify most patients.
