PIGL deficiency is caused by germline mutation in PIGL. PIGL is essential for the second step in biosynthetic pathway of GPI anchor. GPI acts as a membrane anchor of more than 150 human proteins, which serve critical functions as adhesion molecules, receptors, complement regulators, enzymes and co-receptors in signal transduction pathways. The main clinical features are intellectual disability, developmental delay, epilepsy, and sometimes with multisystem disorder such as liver, renal, cardiac and eye involvement. The prevalence of PIGL deficiency is unknown as it is recently recognized disease, but there have been over 17 patients reported. The PIGL gene is located on chromosome 17p11.2, and PIGL deficiency is an autosomal recessive disorder.