CXCR4 and WHIM syndrome: Nearly all cases of WHIM syndrome are attributed to heterozygous autosomal dominant mutations in the C-X-C chemokine receptor type 4 (CXCR4) gene (4), CXCR4 is widely expressed across various cell types, including mature leukocyte subtypes, epithelial cells, endothelial cells, hematopoietic progenitors, stromal fibroblasts, and cancer cells (5, 6).