PIGT and multiple congenital anomalies-hypotonia-seizures syndrome 3: Multiple congenital anomalies–hypotonia–seizures syndrome 3 (MCAHS3) [OMIM:615398] is an AR CDG that originates from homozygous mutations on chromosome 20q13.12 in the phosphatidylinositol-glycan biosynthesis class T (PIGT) gene.