Nonsynonymous mutations in CXCR4 in CLL and WHIM syndrome. Nonsynonymous mutations identified in CLL (chronic lymphocytic leukemia) patients are indicated at their relative positions as sequence traces with corresponding amino acid substitutions. Sites of truncating mutations associated with WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome are also shown.^15,18  Cross-species sequence conservation is shown for the SNPs postulated to be functionally deleterious.