CXCR4 and Decreased total monocyte count: Indeed, WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome, an autosomal dominant disorder often accompanied by monocytopenia, is caused by a single amino acid mutation in CXCR4, which blocks its endocytosis and therefore increases CXCR4 activity [32]}.