Review of the reported patients with MED13L haploinsufficiency indicates moderate to severe ID and facial anomalies in all patients, as well as severe speech delay and muscular hypotonia in the majority.
PRRT2 is a candidate gene for ASD since homozygote mutations are associated with intellectual disability and heterozygote mutations cause benign infantile seizures, paroxysmal dyskinesia, or hemiplegic migraine.
Beyond these clinical entities, PRRT2 mutations have been described in other childhood-onset movement disorders, different forms of seizures, headache disorders, and intellectual disability.
PRRT2 mutations are associated with a wide range of clinical syndromes: the various paroxysmal dyskinesias, infantile seizures, paroxysmal torticollis, migraine, hemiplegic migraine, episodic ataxia and even intellectual disability in the homozygous state.
This family provides strong evidence that homozygous PRRT2 mutations give rise to more severe clinical disease of mental retardation, episodic ataxia, and absences, and, thus, enlarges the clinical spectrum related to PRRT2 mutations.
This report describes the first putative mutations, p.L70P and p.R450C, in the coding region of the UROC1 gene in a girl with urocanic aciduria presenting with mental retardation and intermittent ataxia.
The X-linked creatine transporter deficiency (CRTD) caused by an SLC6A8 mutation represents the second most common cause of X-linked intellectual disability.
Consistent with this notion is the recent demonstration that MECP2 mutations cause Rett syndrome (RTT, MIM 312750), a childhood neurological disorder that represents one of the most common causes of mental retardation in females.
The remaining four had chromosomal rearrangements: an unbalanced translocation, t(11;13), with a deletion including the WAGR (Wilms' tumor, aniridia, genitourinary abnormalities, and mental retardation) region, and three balanced rearrangements with what appear to be position effect breakpoints 3' of PAX6: (a) a t(7;11) with the 11p13 breakpoint approximately 30 kb downstream of PAX6, (b) a dir ins(12;11) with a breakpoint >50 kb from PAX6, and (c) an inv(11)(p13q13) with a breakpoint >75 kb downstream of PAX6.
This study examined the effects of sedation on auditory brainstem response interpeak latency intervals (i.e., I-III, III-V, and I-V) in two groups: (1) a group with Rett syndrome who were positive for mutations in the MECP2 gene and (2) a group negative for mutations in the MECP2 gene but who were severely to profoundly delayed with other causes of mental retardation.
The purpose of this study was to investigate the role of evolutionarily conserved cis-elements in regulating the post-transcriptional expression of the MECP2 gene and to explore their possible correlations with a mutation that is known to cause mental retardation.
Mutations in MECP2 cause classic or preserved speech variant Rett syndrome and intellectual disability in females and early demise or marked neurodevelopmental handicap in males.
Frame shift mutations of the polyglutamine binding protein-1 (PQBP1) gene lead to total or partial truncation of the C-terminal domain (CTD) and cause mental retardation in human patients.