Xu Y, Zhang Z, Yue H, et al. - Given that primary hypertrophic osteoarthropathy (PHO) is a rare disease inherited as a recessive or irregular dominant trait and described by digital clubbing, pachydermia and periostosis, researchers sought to examine five other PHO families with probands carrying SLCO2A1 biallelic mutations and demonstrated that parents with SLCO2A1 monoallelic mutations also displayed PHO manifestations. The results support the hypothesis that SLCO2A1 monoallelic mutations trigger PHO autosomal dominant and broaden the phenotypic spectrum of PHO.