CTSK and osteopetrosis: The genetic basis of osteopetrosis was previously reported from multiple studies in osteopetrosis cohort, and the disease‐causing genes were classified into osteoclast‐rich group (TCIRG1, CLCN7, OSTM1, SNX10, PLEKHM1, FERMT3, LRRK1, MITF, C16orf57, CAII, RELA, CTSK, NEMO, and IKBKG) and osteoclast‐poor group (RANKL, RANK, SLC29A3, TRAF6, and CSF1R; Penna et al., 2019; Sobacchi et al., 2013).