Versatile anomalies and symptoms in these patients are related to the vital biological function of the PNP enzyme and purine metabolites.2 Fewer than half of PNP deficiency patients develop autoimmune diseases, notably systemic lupus erythematosus, idiopathic thrombocytopenic purpura and autoimmune hemolytic anemia, while both patients in this study suffered from anemia.12,13 It has been suggested that PNP deficiency results in increased activation of TLR7 and subsequently IL-6 up-regulation leading to autoimmunity.14 Here, PNP is linked to autoimmune disease.