Abstract: Objective To analyze and summarize the clinical, EEG and genotype characteristics of three children with multiple congenital malformation hypotonia epilepsy syndrome type 2 (MCAHS 2 ). Method The clinical data of three children with MCAHS2 diagnosed in our hospital since March 2017 were collected. Peripheral blood samples of 3 children and their parents were collected for whole exo sequencing, and Sanger sequencing was used to confirm the candidate variants. Results All the three children were boys with onset age of 10 months, the types of epileptic seizures were focal seizures and focal secondary generalized seizures. In addition, child three had myoclonic seizures, children one and three had status epilepticus, and children one and two had strong heat sensitivity. All the three children had different degrees of intellectual disability, facial dysmorphism and brain MRI abnormalities. EEG showed diffuse slow waves in the background, multifocal spikes in the interval or mixed with focal discharges. Variants in PIGA was found in all three children, and the variants were c. 713 A>G（p.K238R）、c. 241C>T (p.R81C) and c. 356G>A（p.R119Q), respectively. Conclusion MCAHS 2 is a rare disease with X-linked recessive inheritance which mainly caused by missense mutation in PIGA. The clinical phenotype is extensive, the epileptic seizure form is diverse, and has certain heat sensitivity. EEG showed various patterns.

Key words: PIGA gene; multiple congenital malformations; hypotonia; epilepsy; glycosylphosphatidylinositol