An ASD "comorbidity" can have several fundamentally-distinct causal origins: it can arise due to shared genetic risk between ASD and non-ASD phenotypes (e.g., ASD and microcephaly in the context of the MECP2 mutation), as a "secondary symptom" of ASD when engendered by the same causal influence (e.g., epilepsy in channelopathies associated with ASD), due to chance co-occurrence of ASD with a causally-independent liability (e.g., ASD and diabetes), or as the late manifestation of an independent causal influence on ASD (eg, attention-deficit/hyperactivity disorder).
Loss-of-function mutations of the MECP2 gene are the cause of most cases of Rett syndrome in females, a progressive neurodevelopmental disorder characterized by severe mental retardation, global regression, hand stereotypies, and microcephaly.
We screened the FOXG1 gene in a cohort of 206 MECP2 and CDKL5 mutation negative patients (136 females and 70 males) with severe encephalopathy and microcephaly.
Rett syndrome (RTT), an X-linked, dominant neurodevelopmental disorder caused by mutations in the methyl-CpG-binding protein 2 (MECP2) gene, presents with acquired microcephaly, autistic regression, hand usage loss, and stereotypies.
Rett syndrome (RS) is an X-linked dominant neurodevelopmental disorder caused by mutations in MECP2 (Xq28) and characterized by normal development until 6-12 months of age, followed by regression with loss of acquired skills, gradual onset of microcephaly, stereotypic hand movements and psychomotor delay.