Primary hypertrophic osteoarthropathy(PHO)is a rare disease also known as pachydermo-periostosis.We reported a painless case whose diagnosis was confirmed by genetic test.A 24-year-old male presented a series of symptoms that first began at 14.He suffered from progressive clubbed-fingers accompa-nied by swelling of the wrist and ankle joints.Facial skin concentric thickening and alar nose broadening ap-peared simultaneously and increased progressively.He was also prone to acne and hyperhidrosis.X-rays showed thickening of the metacarpal and phalangeal bones,as well as symmetrical periosteal ossification of both the tibia and fibula.Clinical diagnosis of PHO is difficult because of the variable features.With acromeg-aly excluded,the diagnosis was confirmed by a genetic test.Whole exome sequencing revealed a heterozygous SLCO2A1 c.611C＞T(p.Ser204Lue)and SLCO2A1 c.1602C＞A(p.Asn534Lys)mutation from each par-ent.It suggests that primary hypertrophic osteoarthropathy should be considered for young limb hypertrophic patients especially when periosteal thickening signs were showed in X-ray.A confirmatory diagnosis can be made through the genetic test.