CXCR4 and WHIM syndrome: Conversely, a defective monomer may adversely affect the function of the dimer, as the primarily heterozygous disease WHIM syndrome (warts, hypogammaglobulinemia, infections, and myelokathexis syndrome) presents with coexpression of a truncated CXCR4 that exerts dominance over the expressed wild-type receptor [41].