NCIthesaurus MHC class II deficiency A severe combined immunodeficiency that is characterized by deficiency of MHC class II molecules that causes lack of immune protection against bacteria, viruses, and fungi and thus causes early death in childhood, and has_material_basis_in autosomal recessive inheritance of mutation in the CIITA, RFX5, RFXANK, and RFXAP genes. BLSII UMLS_CUI:C0242583 ICD10CM:D81.6 SNOMEDCT_US_2025_09_01:71904008 MIM:209920 MESH:D016511 NCI:C3895 disease_ontology DOID:5812 OMIM mapping confirmed by DO. [SN]. SCID due to absent class II HLA antigens bare lymphocyte syndrome type II severe combined immunodeficiency