This miR, indeed, shares the same role as IL-21 in B cell differentiation and could lead to two different phenotypes: One with typical recurrent infections and a better outcome, and one characterized by non-infectious complications, such as splenomegaly and autoimmune and neoplastic diseases, as found in IL-21 KO mouse models [37,38]. The gene discussed is IL21; the disease is Splenomegaly.