Our approach was a practical one given the size of LRP5 and exon 2 of SOST. We did not sequence for DKK1 mutations; a novel missense mutation in the LRP5 inhibitor DKK1 (c.74Y>F) has recently been reported to segregate with HBM in one Spanish family.59 Nor did we sequence CLCN7 (associated with autosomal dominant osteopetrosis type 2) or genes associated with the more severe autosomal recessive forms of osteopetrosis (eg, TNFSF11s, TCIRG1, and PLEKHM1) because clinical and radiological phenotyping excluded diagnoses of osteopetrosis. The gene discussed is DKK1; the disease is osteopetrosis.