Glucose-6-phosphate isomerase (GPI) has many other names, including Phosphohexose isomerase (PHI), Neuroleukin (NLK) and Spermantigen-36 (SA-36). GPI is a cytoplasmic homodimer belonging to the GPI family. It is a neurotrophic factor for spinal and sensory neurons and is involved in glycolysis and gluconeogenesis. Defects or mutations in GPI can cause hereditary nonspherocytic hemolytic anemia (HA), hydrops fetalis, immediate neonatal death and neurological impairment.