| Disease ID | Source | Name | Description |
| 300260 | OMIM | Mental retardation, X-linked, syndromic, Lubs type (MRXSL) | A disorder characterized by significantly below average general intellectual functioning associated with impairments in adaptive behavior and manifested during the developmental period. MRXSL patients manifest mental retardation associated with variable features. They include swallowing dysfunction and gastroesophageal reflux with secondary recurrent respiratory infections, hypotonia, mild myopathy and characteristic facies such as downslanting palpebral fissures, hypertelorism and a short nose with a low nasal bridge. The disease is caused by variants affecting the gene represented in this entry. Increased dosage of MECP2 due to gene duplication appears to be responsible for the mental retardation phenotype. |
| 300055 | OMIM | Mental retardation, X-linked, syndromic, 13 (MRXS13) | A disorder characterized by significantly below average general intellectual functioning associated with impairments in adaptive behavior and manifested during the developmental period. MRXS13 patients manifest mental retardation associated with other variable features such as spasticity, episodes of manic depressive psychosis, increased tone and macroorchidism. The disease is caused by variants affecting the gene represented in this entry. |
| 300673 | OMIM | Encephalopathy, neonatal severe, due to MECP2 mutations (ENS-MECP2) | A neurodevelopmental disorder characterized by severe neonatal encephalopathy, developmental delay, mental retardation, microcephaly, seizures. Additional features include respiratory insufficiency and central hypoventilation, gastroesophageal reflux, axial hypotonia, hyperreflexia and dyskinetic movements. The disease is caused by variants affecting the gene represented in this entry. The MECP2 gene is mutated in Rett syndrome, a severe neurodevelopmental disorder that almost always occurs in females. Although it was first thought that MECP2 mutations causing Rett syndrome were lethal in males, later reports identified a severe neonatal encephalopathy in surviving male sibs of patients with Rett syndrome. Additional reports have confirmed a severe phenotype in males with Rett syndrome-associated MECP2 mutations. |
| 312750 | OMIM | Rett syndrome (RTT) | An X-linked dominant neurodevelopmental disorder, and one of the most common causes of mental retardation in females. Patients appear to develop normally until 6 to 18 months of age, then gradually lose speech and purposeful hand movements, and develop microcephaly, seizures, autism, ataxia, mental retardation and stereotypic hand movements. After initial regression, the condition stabilizes and patients usually survive into adulthood. The disease is caused by variants affecting the gene represented in this entry. |
| 300496 | OMIM | Autism, X-linked 3 (AUTSX3) | A complex multifactorial, pervasive developmental disorder characterized by impairments in reciprocal social interaction and communication, restricted and stereotyped patterns of interests and activities, and the presence of developmental abnormalities by 3 years of age. Most individuals with autism also manifest moderate mental retardation. The disease may be caused by variants affecting the gene represented in this entry. |
| 105830 | OMIM | Angelman syndrome (AS) | A neurodevelopmental disorder characterized by severe motor and intellectual retardation, ataxia, frequent jerky limb movements and flapping of the arms and hands, hypotonia, seizures, absence of speech, frequent smiling and episodes of paroxysmal laughter, open-mouthed expression revealing the tongue. The disease may be caused by variants affecting the gene represented in this entry. |