Less frequent osteopetroses (5% of ARO cases) present mutations in the osteoclastogenesis-associated transmembrane protein 1 (OSTM1) gene, encoding a highly glycosylated protein at its N-terminus able to stabilize ClC-7 and complement its activity at the ruffled border (Chalhoub et al., 2003; Leisle et al., 2011). Here, CLCN7 is linked to osteopetrosis.