DDX3X syndrome
Incidence
Is caused by a spontaneous mutation at conception; nothing either parent did caused their child’s condition. Primarily affects girls due to its location on the X-chromosome, though there are affected boys. It was only recently discovered in 2014. Has only been identified in about 200 individuals, however, many doctors believe it is the cause of 1 to 3 percent of all intellectual disabilities in females.
Clinical Characteristics
Analysis of the clinical data in 38 patients evaluated in 2015 suggested a syndromic disorder with variable clinical presentation. The females evaluated (age range 1–33 years) showed varying degrees of intellectual disability (ID) (mild to severe) or developmental delay with associated neurological abnormalities, including hypotonia (29/38, 76%), movement disorders comprising dyskinesia, spasticity, and a stiff-legged or wide-based gait (17/38, 45%), microcephaly (12/38, 32%), behavior problems including autism spectrum disorder (ASD), hyperactivity, and aggression (20/38, 53%), and epilepsy (6/38, 16%). Several recurrent additional features were noted, including joint hyperlaxity, skin abnormalities (mosaic-like pigmentary changes in some females), cleft lip and/or palate, hearing and visual impairment, and precocious puberty. Abnormal brain MRIs were reported in various females, with corpus callosum hypoplasia (13/37, 35%), ventricular enlargement (13/37, 35%), and evidence of cortical dysplasia (e.g., polymicrogyria) in four individuals. Although common dysmorphic features are reported, there is no consistent recognizable phenotype. Also there is no evidence for an obvious genotype-phenotype correlation between the different types of mutations and degree of ID.
Precipitants
None. They do not have any specific crisis.
Provocation Tests
None
Diagnostic Procedures
It is most probable a clinical diagnosis but it is often misdiagnosed as autism spectrum disorder, cerebral palsy, Rett Syndrome, Dandy Walker Syndrome, or a generic developmentally delayed label. Most cases have been diagnosed after running WES (whole exon sequence analysis) showing mutations in DDX3X gene.