| Disease ID | Source | Name | Description |
| 616917 | OMIM | Mental retardation, autosomal recessive 53 (MRT53) | A form of mental retardation, a disorder characterized by significantly below average general intellectual functioning associated with impairments in adaptive behavior and manifested during the developmental period. Most MRT53 patients manifest severely delayed psychomotor development, hypotonia, and early-onset seizures. Additional features, such as cerebellar hypoplasia and ataxia have been observed in some patients. The disease is caused by variants affecting the gene represented in this entry. Cells from patients carrying PIGG disease-causing mutations show abnormal accumulation of the GPI precursors H7 and H7' and absence of mature GPI precursor H8, consistent with a loss of function. However, GPI-anchored proteins, including CD59, CD55, CD24 and CD16, are normally expressed at the cell surface of lymphocytes and granulocytes and CD59 exhibits sensitivity to bacterial phosphatidylinositol-specific phospholipase C, suggesting a normal structure. The role of PIGG in MRT53 etiology is not clear. |