PFN1 and bone Paget disease: We recently identified a loss-of-function mutation in the PFN1 gene (c.318_321del) in a hereditary form of OS arising in Paget’s disease of bone, and somatic PFN1 loss of heterozygosity (LOH) was also detected in sporadic OS/PDB patients26, thus suggesting a potential role for Profilin 1 in OS pathogenesis.