Abstract
BACKGROUND: Tumor-induced osteomalacia is an uncommon paraneoplastic syndrome caused by Fibroblast growth factor-23-secreting tumors. It is characterized by phosphaturia, hypophosphatemia, and a high plasma level of alkaline phosphatase. CASE PRESENTATION: We report a young patient with psoriasis who had suffered from bone pain and muscle weakness for more than 6.5 years. He was finally diagnosed with tumor-induced osteomalacia. However, mistakenly attributing the patient's signs and symptoms to psoriatic arthritis for a long time had resulted in multiple complications for the patient. Finally, the tumor was localized and surgically resected. This resulted in clinical improvements and the resolution of all biochemical abnormalities. CONCLUSION: To our knowledge, this is the second case of tumor-induced osteomalacia accompanied by psoriasis. There is growing evidence to suggest that Fibroblast growth factor-23 has a role in regulating immune function while an increased level of it may play a role in the pathogenesis of psoriasis. As a result, tumor-induced osteomalacia may affect the psoriasis clinical course by secreting a high amount of Fibroblast growth factor-23. On the other hand, several studies have showed an increased risk of malignancy among patients with psoriasis. Consequently, long-term psoriasis may predispose patients to Fibroblast growth factor-23-secreting tumors. Finally, as psoriasis is a common disease, this presentation may simply be a coincidence.