Primary hypertrophic osteoarthropathy

Primary hypertrophic osteoarthropathy (PHO), also known as pachydermoperiostosis or Touraine-Solente-Golé syndrome, is a rare genetic disorder characterized by a triad of clinical features: digital clubbing (enlargement of the fingertips and toes), periostosis (abnormal new bone formation along the long bones), and pachydermia (thickening and coarsening of the skin, particularly of the face and scalp). The condition primarily affects the skeletal system, skin, and joints. Patients often develop deep furrows on the forehead and scalp (cutis verticis gyrata), excessive sweating (hyperhidrosis), and seborrhea (oily skin). Joint pain and swelling, particularly of the knees, ankles, and wrists, are common and can be debilitating. The disease typically manifests around puberty and progresses over the following decade before stabilizing. PHO is caused by mutations in genes involved in prostaglandin E2 (PGE2) metabolism. Two major genetic forms have been identified: mutations in the HPGD gene (encoding 15-hydroxyprostaglandin dehydrogenase) and mutations in the SLCO2A1 gene (encoding a prostaglandin transporter). Both result in elevated levels of PGE2, which drives the periosteal bone formation, skin changes, and other clinical manifestations. The condition predominantly affects males, and when it occurs in females, the presentation tends to be milder (an incomplete form). Treatment of PHO is primarily symptomatic and supportive. Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to manage joint pain and inflammation. In some cases, selective COX-2 inhibitors or corticosteroids may be employed. Surgical interventions, including cosmetic procedures for severe pachydermia or orthopedic procedures for joint complications, may be considered. Etoricoxib and other agents targeting the prostaglandin pathway have shown some benefit in reducing symptoms. There is currently no cure for the condition, and management focuses on improving quality of life and addressing specific symptoms as they arise.

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