MedGen

Nonspecific X-linked intellectual deficiencies (MRX) belong to the family of sex-linked intellectual deficiencies (XLMR). In contrast to syndromic or specific X-linked intellectual deficiencies (MRXS), which also present with associated physical, neurological and/or psychiatric manifestations, intellectual deficiency is the only symptom of MRX. [from MONDO]

Disorders of intracellular cobalamin metabolism have a variable phenotype and age of onset that are influenced by the severity and location within the pathway of the defect. The prototype and best understood phenotype is cblC; it is also the most common of these disorders. The age of initial presentation of cblC spans a wide range: In utero with fetal presentation of nonimmune hydrops, cardiomyopathy, and intrauterine growth restriction. Newborns, who can have microcephaly, poor feeding, and encephalopathy. Infants, who can have poor feeding and slow growth, neurologic abnormality, and, rarely, hemolytic uremic syndrome (HUS). Toddlers, who can have poor growth, progressive microcephaly, cytopenias (including megaloblastic anemia), global developmental delay, encephalopathy, and neurologic signs such as hypotonia and seizures. Adolescents and adults, who can have neuropsychiatric symptoms, progressive cognitive decline, thromboembolic complications, and/or subacute combined degeneration of the spinal cord. [from GeneReviews]

A mode of inheritance that is observed for traits related to a gene encoded on the X chromosome. [from HPO]

An X-linked dominant condition caused by mutation(s) in the IQSEC2 gene, encoding IQ motif and SEC7 domain-containing protein 2. It is characterized by substantially impaired intellectual functioning and behavioral abnormalities. [from NCI]

Nonsyndromic mental retardation with a large head, relatively short stature, highly arched palate, square facies, short hands and feet, and macroorchidism. [from MCA/MR]