Glycosylphosphatidylinositol (GPI) glycolipids play a critical role in the post-translation modification and cell membrane anchoring of > 150 eukaryotic proteins which ultimately affect the sorting, trafficking, and dynamics of those proteins. Also, they participate in the process of embryogenesis, neurogenesis, immune responses, and fertilization. The biogenesis of mature GPI involves > 20 genes and occurs in eukaryotes via a conserved post-translational pathway [1]. In animal studies, complete deletion of the GPI pathway results in embryonic lethality. However, complete deletion has not been reported in humans. Hypomorphic mutations in the genes encoding the GPI biogenesis pathway result in partial reduction of GPI-anchored proteins, which leads to phenotypically heterogeneous clinical presentations, with global developmental delay a common feature. This element supports the notion that GPI-anchored proteins play a vital role in neurogenesis [2,3]. PIGL encodes the endoplasmic phosphatidylinositol glycan anchor biosynthesis class L, which is involved in the second step of GPI biosynthesis: the de-n-acetylation of n-acetylglucosaminyl-phosphatidylinositol (GluNAc-PI), generating glucosaminyl-phosphatidylinositol (GlcN-PI) on the cytoplasmic side of the endoplasmic reticulum [4]. Mutations in PIGL have been linked to two rare distinctive syndromes: CHIME syndrome (Zunich neuroectodermal syndrome) and Mabry syndrome (hyperphosphatasia with mental retardation syndrome, HPMRS) [5,6].

۲٫ Clinical data

The proband is a 10-year-old West African male who is the first offspring of a non-consanguineous couple. He was delivered spontaneously at term after an uneventful pregnancy weighing 2665 g (5th percentile) with a head circumference of 32 cm (5th percentile) and Apgar score of 9. At the age of 6 months, he presented with myoclonic seizures that were partially controlled with medications. By the age of 12 months, he had surgical correction of inguinal hernia, hydrocele, and strabismus. His developmental milestones were globally delayed, including cognitive, language, gross and fine motor functions, with no major improvement despite intensive rehabilitation. His first available baseline physical examination was documented at 4 years of age. Growth parameters were normal with weight, height and head circumference on the 75th percentile. The facial features were coarsely dysmorphic, including prominent forehead, high arched eyebrows and sparse on the outer third, nystagmus, mild telecanthus, uplifted ear lobes, and open mouth with intermittent drooling. In addition, he had mild pectus excavatum and clinodactyly involving the fifth digits,