Primary immunodeficiency diseases are inborn errors in the immune system due to defective genes. Certain of these disorders are sometimes or often associated with hypereosinophilia. The list of such disorders includes ZAP70 deficiency (defective "ZAP70" gene), CD3gamma chain deficiency (defective "CD3G" gene), MCHII deficiency (defective "RFXANK" gene), Wiskott–Aldrich syndrome (defective "WAS" gene), IPEX syndrome (defective "IPEX" gene), "CD40" gene defect, and autoimmune lymphoproliferative syndrome (defective "Fas receptor" gene). More than 30 other primary immunodeficiency diseases are sometimes associated with modest increases in eosinophil counts, i.e. eosinophilia. The hyperimmunoglobulin E syndrome is associated with hypereosionphilia or eosinophilia due to mutations in any one of the following genes: "STAT3, DOCK8, PGM3, SPINK5", and "TYK2" (see mutations in the hymperimmoglobulin E syndrome). Omenn syndrome is a severe combined immunodeficiency disease characterized by skin rash, slenomegaly, and lymphadenopathy due to a causative mutation in "RAG1, RAG2", or, more rarely, one of several other genes.