- CD59 deficiency is a common finding in red and white blood cells in patients with chronic hemolysis suffering from paroxysmal nocturnal hemoglobinuria (PNH) where acquired mutation in the PIGA gene leads to membrane loss of GPI-anchored membrane proteins, including CD59. The current study objective was the elucidation of the molecular basis of childhood familial chronic Coombs' negative hemolysis and relapsing polyneuropathy, presenting as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) in infants of North-African Jewish origin from four unrelated families. A founder mutation was searched using homozygosity mapping followed by exome sequencing. The expression of CD59, CD55 and CD14 was examined in blood cells by flow cytometry followed by western blot of the CD59 protein. A homozygous missense mutation, p.Cys89Tyr in CD59, was identified in all the patients. The mutation segregated with the disease in the families and had a carrier rate of 1:66 among Jews of North-African origin. The mutated protein was present in the patients' cells in reduced amount and was undetectable on the membrane surface. The Cys89Tyr mutation in CD59 is associated with a failure of proper localization of CD59 protein in the cell surface. This is clinically manifested in infancy by chronic hemolysis and relapsing peripheral demyelinating disease.