Persistent Hypophosphatemic Osteomalacia Secondary to a Skull Base Mesenchymal Tumor: A Case Report and Review of Literature

Oncogenic Osteomalacia is rare yet a recognised set of disorders that mimic rickets but are resistant to medical management. They are seen in a variety of tumors of the CNS including hemangiopericytomas, bony tumors, and meningiomas. The most common cause however is a Mesenchymal secretory tumor resembling a fibroma sitting in the base of the skull near the nasal sinuses. These tumors are seen to secrete Fibroblast Growth Factor 23 (FGF-23) which mimics parathyroid hormone leading to a Hypophosphatemic hypercalcaemic picture characterised by body aches, recurrent fractures, growth retardation, deformities, and proximal myopathy.

We report a case of tumor-induced osteomalacia caused by an infratemporal skull base tumor. The tumor was successfully resected via a subtemporal epidural approach. Phosphate level recovered immediately after resection. A review of relevant literature over the past 10 years as well as newer methods to diagnose and treat these rare entities are mentioned.