Genetic studies have identified the impaired prostaglandin (PGE2) metabolism as the leading cause of PHO, specifically due to biallelic mutations in the HPGD gene (MIM*606188) encoding 15-hydroxyprostaglandin dehydrogenase (15-PGDH) or the SLCO2A1 gene (MIM*601460) encoding the prostaglandin transporter (PGT) (Li et al., 2017). The gene discussed is HPGD; the disease is primary hypertrophic osteoarthropathy.