On investigation, he was found to have direct Coombs test (DCT+) anemia (9 g/dL), hypergammaglobulinemia (2857 mg/dL), mild CD4 lymphopenia with severe reduction in naïve CD4 cells (11%), and very low Treg cells (0.6% of CD4 cells estimated by CD25+CD127 low cells, suggestive of near absence of CD25 expression) with normal DNT and benign reactive lymph nodes on histopathology. The gene discussed is CD4; the disease is anemia (phenotype).