proteins include enzymes, adhesion molecules, receptors, and regulatory proteins of the immune system. 4 Recently, PIGN has been shown to also mediate protein quality control within ER, contributing to maintaining chromosomal stability. 5,6 Biallelic disease-causing variants in genes involved in the GPI synthesis pathway have been associated with epilepsy, developmental delay (DD), intellectual disability (ID), hypotonia, and multiple congenital anomalies affecting different organs. 2,7 Forty-three patients with PIGN diseases from 32 families with 42 unique PIGN variants, including 10