Sporadic hypophosphatemic osteomalacia combined with psoriasis: A rare case report and a brief review of the literature.

Background: Hypophosphatemic osteomalacia (HO) is an unusual metabolic disease characterized by low concentrations of serum phosphate levels, which leads to reduced mineralization of the bone matrix. Typically, HO consists of 4 common types: X-linked dominant hypophosphatemia (XLH), autosomal dominant hypophosphatemic rickets (ADHR), tumor-induced osteomalacia (TIO), and sporadic HO.

Case Presentation: We herein report the case of a 48-year-old man who developed multiple joint and bone pain and muscle weakness over 5 months with a 23-year history of psoriasis. He was diagnosed with psoriatic arthritis by primary hospitals but was unresponsive to etanercept and adalimumab treatments. After referral to our hospital, the patient was diagnosed with HOs combined with psoriasis. The patient was treated with oral phosphate solution, calcium, and active vitamin D, and the symptoms of bone and joint pain and muscle weakness gradually relieved. Since TIO accounts for the majority of adult-onset HO, positron emission tomography - computed tomography or octreotide imaging examinations had been done yearly to locate any underlying tumor in our patient, with negative findings in the 4-year follow-up.

Conclusions: Diagnosis of HO remains a challenge to rheumatologists, and especially to dermatologists when accompanied by psoriasis. After excluding the inherited HO and with negative tumor, this report may be the first male case of sporadic HO combined with psoriasis.