PIGN, Phosphatidylinositol glycan anchor biosynthesis class N, is involved in glycosylphosphatidylinositol (GPI)-anchor biosynthesis in the endoplasmic reticulum, which is crucial for the proper functioning of many cell-surface proteins. It also has a non-canonical function in preventing protein aggregation in the endoplasmic reticulum independently of GPI-anchor biosynthesis [4].

Mutations in PIGN are associated with multiple congenital anomalies-hypotonia-seizures syndrome 1 (MCAHS1), Fryns syndrome, and various neurologic phenotypes. Patients with biallelic PIGN variants often present with epilepsy, developmental delay, and hypotonia. For instance, 26 patients with biallelic PIGN variants had a wide spectrum of epilepsy phenotypes, and most had profound to severe developmental impairment [1]. In another case, a 16-year-old girl with a compound heterozygous variant in PIGN had epilepsy, developmental delay, and cerebellar atrophy [2]. Also, three individuals from two Lithuanian families with PIGN genotypes consistent with MCAHS1 showed a range of phenotypic features [3].

In conclusion, PIGN is essential for GPI-anchor biosynthesis and protein quality control in the endoplasmic reticulum. Research on PIGN-related genetic mutations in patients has revealed its significant role in multiple congenital anomaly-seizure-related syndromes and various neurologic conditions. Understanding PIGN's functions through these patient-based genetic studies provides insights into the molecular mechanisms underlying these diseases, potentially guiding future diagnostic and therapeutic strategies.