Mutations causing LRP4 HBM occur in the central cavity of the third β-propeller domain of the LRP4 protein, impairing the interaction between sclerostin and LRP4 (119) (of note mutations elsewhere in LRP4 are associated with Cenani-Lenz Syndactyly Syndrome, MIM212780) (Figure 1). Here, LRP4 is linked to Cenani-Lenz syndactyly syndrome.