MedGen

Neurodevelopmental disorder with epilepsy and hemochromatosis (NEDEPH) is an X-linked recessive disorder characterized by global developmental delay, early-onset seizures, and progressive systemic iron deposition particularly affecting the liver and resulting in juvenile-onset hemochromatosis. Variable additional features may include joint contractures, visual or hearing impairment, and skin abnormalities (summary by Swoboda et al., 2014 and Muckenthaler et al., 2022). [from OMIM]

Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon acquired hemolytic anemia that often manifests with hemoglobinuria, abdominal pain, smooth muscle dystonias, fatigue, and thrombosis. The disease results from the expansion of hematopoietic stem cells harboring a mutation in the PIGA gene, which encodes a protein required for the biosynthesis of glycosylphosphatidylinositol (GPI), a lipid moiety that attaches dozens of proteins to the cell surface. Thus, PNH cells are deficient in cell surface GPI-anchored proteins. This deficiency on erythrocytes leads to intravascular hemolysis, since certain GPI-anchored proteins (i.e., CD55 (125240) and CD59 (107271)) normally function as complement regulators. Free hemoglobin released from intravascular hemolysis leads to circulating nitrous oxide depletion and is responsible for many of the clinical manifestations of PNH, including fatigue, erectile dysfunction, esophageal spasm, and thrombosis (review by Brodsky, 2008). Genetic Heterogeneity of Paroxysmal Nocturnal Hemoglobinuria See also PNH2 (615399), which may be caused by germline and somatic mutation in the PIGT gene (610272) on chromosome 20q13. [from OMIM]

Multiple congenital anomalies-hypotonia-seizures syndrome-2 (MCAHS2) is an X-linked recessive neurodevelopmental disorder characterized by dysmorphic features, neonatal hypotonia, early-onset myoclonic seizures, and variable congenital anomalies involving the central nervous, cardiac, and urinary systems. Some affected individuals die in infancy (summary by Johnston et al., 2012). The phenotype shows clinical variability with regard to severity and extraneurologic features. However, most patients present in infancy with early-onset epileptic encephalopathy associated with developmental arrest and subsequent severe neurologic disability; these features are consistent with a form of developmental and epileptic encephalopathy (DEE) (summary by Belet et al., 2014, Kato et al., 2014). The disorder is caused by a defect in glycosylphosphatidylinositol (GPI) biosynthesis. For a discussion of genetic heterogeneity of MCAHS, see MCAHS1 (614080). For a discussion of nomenclature and genetic heterogeneity of DEE, see 308350. For a discussion of genetic heterogeneity of GPI biosynthesis defects, see GPIBD1 (610293). [from OMIM]