Depending on the arrangement of conserved N‐terminal cysteine residues, chemokines are classified into CXC, CC, C, or CX3C subfamilies.(7) Various chemokines and chemokine receptors are critical for bone homeostasis and osteoclastogenesis.(8) In particular, CCR1‐deficient mice exhibit osteopenia due to impaired osteoclast and osteoblast function.(9) CCR2 is expressed in the osteoclast lineage, and CCR2‐deficient mice show osteopetrosis resulting from markedly reduced numbers of mature osteoclasts.(10) Moreover, female CCR2‐deficient mice are resistant to ovariectomy‐induced osteoporosis.(10). The gene discussed is CCR2; the disease is Osteopenia.