TNFSF11 and osteopetrosis: Although approximately 30% of the etiology of human osteopetrosis remain genetically unrecognized, but so far, at least 20 genes mutation including TCIRG1, CLCN7, SNX10, OSTM1, PLEKHM1, CAII, FERMT3,RANKL, RANK( TNFRSF11), SLC29A3, TRAF6,LRRK1,MITF, NEMO, RELA,CSF1R,C16ORF57,CTSK,Kindlin-3,CalDAG-GEFI, have been reported to associated with human osteopetrosis [3–6].