Primary hypertrophic osteoarthropathy (HOA) is a rare condition with no identifiable cause, accounting for 3%-5% of all HOA cases. It is challenging to identify incomplete primary HOA, which can be misdiagnosed as other hypertrophic periostitis diseases. At least two of the four criteria set by Borochowitz and Rimoin (1990) must be present to diagnose primary HOA. Diagnostic difficulties due to incomplete or atypical manifestations are common. We present a case of incomplete primary PHOA at Hanoi Medical University Hospital in Vietnam. A 37-year-old male presented with ankle joint pain for nearly four years. X-ray and magnetic resonance imaging showed periostitis in the tibias and fibulas, which could not exclude Camurati-Engelmann disease. Finally, gene sequencing on the Illumina MiSeq system identified a missense mutation (c.295C>T) in the solute carrier organic anion transporter family member 2A1 (SLCO2A1) gene on chromosome 3. Our case report and literature review aim to improve specialists' understanding of incomplete primary HOA and reduce the frequency of missed diagnoses.  Kulcsszavak: primary hypertrophic osteoarthropathy, gene mutation, c.295C>T, SLCO2A1