Primary Hypertrophic Osteoarthropathy Mimicking Juvenile Idiopathic Arthritis: A Novel SLCO2A1 Mutation and Imaging Findings.

Primary hypertrophic osteoarthropathy (PHO), also known as pachydermoperiostosis, is a rare, multisystemic, autosomal recessive condition typically presenting with digital clubbing, osteoarthropathy, and various skin manifestations. Radiographs show distinctive periosteal reaction and thickening along the long bones. PHO is caused by homozygous mutations in the HPGD gene in chromosome 4q34.1 or the SLCO2A1 gene in 3q22.1q22.2. Here, we report on a 20-year-old male with enlarged and swollen joints with arthralgia, palmoplantar hyperhidrosis, and large hands and feet with marked digital clubbing. We also present radiographic, MRI, and ultrasonographic features of the case. These clinical and imaging findings were compatible with the diagnosis of PHO, and a novel homozygous mutation, c.576C>G, p.Ile192Met, was found in SLCO2A1.