CLCN7 and osteopetrosis: Autosomal-dominant osteopetrosis type II (ADOII) (MIM# 166600), also known as Albers-Schönberg disease, is the most frequent (1:20.000) form of osteopetrosis [2] and is mostly caused by heterozygous-dominant negative mutations of the gene-encoding chloride channel, voltage-sensitive 7 (CLCN7; OMIM #602727) [3–5].