PRPS1 and Lethal ataxia with deafness and optic atrophy: Our work may also help explain observations regarding genetic disorders of the immune compartment such as severe combined immunodeficiency (SCID) [53], Arts syndrome [54], Charcot-Marie-Tooth disease-5 (CMTX5) [55], DFN2 [42] and lupus erythematosus [56] some of which are X-linked disorders arising from mutations in PRPS1 or PRPS2.