The elder sister developed recurrent febrile rashes, oral candidiasis, and locoregional BCGitis with acid-fast bacilli in granulomas, followed by progressive respiratory failure and fatal cytomegalovirus pneumonitis despite antiviral therapy; immunology showed profound CD4+ lymphopenia with CD4/CD8 inversion, near-absent HLA-DR on B cells, undetectable IgG/IgA, and elevated IgM. The gene discussed is CD8A; the disease is oral candidiasis.