Molecule

CXCR4

Chemokine receptor driving bone marrow homing

Expression change
WHIM-like mutations in ~30-40%
Evidence level
established

Role in pathogenesis

CXCR4 is a chemokine receptor for CXCL12 (SDF-1). WHIM-like mutations (most commonly S338X) cause sustained receptor signaling and enhanced bone marrow homing. These mutations are associated with higher IgM, more hyperviscosity, and reduced response to BTK inhibitors.