[Inherited GPI deficiency; a new disease with intellectual disability and epilepsy].

Recently, many cases of inherited GPI deficiency(IGD) are found among individuals with intellectual disability and intractable seizures. To date, about twenty patients have been reported in Japan and up to a hundred in the world. GPI is the glycolipid which anchors 150 kinds of proteins to the plasma membrane. We have found that there are at least 26 genes involved in the biosynthesis or modification of GPI-anchored proteins. IGDs caused by mutations in 12 genes were reported until now. IGD shows a variety of symptoms according to the affected genes and the severity of the mutations. Some patients have hyperphosphatasia and most patients can be diagnosed by the flow cytometric analysis of the blood cells. Early diagnosis and treatment are desirable because the disease progresses even after birth and vitamin B6(pyridoxine) is very effective for some patients with intractable seizures.