PIGF (phosphatidylinositol glycan anchor biosynthesis class F) is a stabilizing subunit of ethanolamine phosphate transferase complexes that catalyzes critical steps in GPI anchor biosynthesis 1. The protein mediates sequential transfer of ethanolamine phosphate groups to mannose residues on GPI anchor intermediates, participating in the tenth and eleventh biosynthetic steps in association with PIGO and PIGG 12. PIGF is localized to the endoplasmic reticulum membrane where it facilitates proper protein anchoring to the plasma membrane 3. The PIGF gene, located on chromosome 2-p21, spans approximately 40 kb across six exons and shows conserved structure and organization across species 34. Mutations in PIGF are associated with onychodystrophy, osteodystrophy, impaired intellectual development, and seizures syndrome, reflecting the critical importance of GPI anchor biosynthesis for neurological and skeletal development. Unlike X-linked PIGA mutations, biallelic PIGF mutations are rare, accounting for limited disease prevalence. PIGF's role in GPI anchor synthesis is essential for surface expression of numerous membrane proteins critical for cellular function.