Various kinds of mutation types were detected among the five individuals with PHO in this study, which included a heterozygous frameshift mutation (c.122delC), a heterozygous nonsense mutation (440G>A), two heterozygous splice-site mutations (c.724+1G>A; c.940+1G>A), a heterozygous missense (p.C594Y) and a homozygous missense (p.R561C) in SLCO2A1. Both the p.R561C and p.C594Y missense mutations are at highly conserved positions and likely to be functionally damaging. The gene discussed is SLCO2A1; the disease is primary hypertrophic osteoarthropathy.