Truncating germline mutations in the C-terminus of CXCR4 have been shown to act as gain-of-function mutations and cause WHIM syndrome (warts, hypogammaglobulinemia, infections, and myelokathexis), and Waldenström’s macroglobulinemia[52]. The gene discussed is CXCR4; the disease is Waldenstrom macroglobulinemia.