A case report of Tumor-Induced Osteomalacia (TIO) caused by central giant cell granuloma

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome defined by severe hypophosphatemia, bone loss, fractures, and muscle weakness. Identifying of the tumor site is often difficult. The primary treatment for Tumor-induced osteomalacia (TIO) is currently surgical resection. Removing the primary tumor is the most definitive treatment for this disease.

Here we describe the case of a 32-year-old man who exhibited sever muscle weakness and pain that had continued for three years. The patient has three sisters and one brother, all of whom are completely healthy and free of bone and muscle problems.Laboratory data indicate low serum phosphorus, normal serum and urine calcium level, besides raised alkaline phosphatase level. Due to elevated phosphorus levels in the urine and the lack of an alternative source for phosphorus excretion, along with the absence of short stature, bone deformities, and a negative family history that might suggest the potential for Tumor-induced osteomalacia (TIO), an octreotide scan was performed to the localized the tumor site. The scan, corroborated by CT and MRI scans, displayed absorption in the right maxillary sinus. Surgical excision of the lesion confirmed it to be a central giant cell granuloma.

Following surgery and without receiving any other treatment, the patient's phosphorus levels and clinical condition improved compared to before the surgical treatment. Subsequently, the symptoms of muscle weakness and skeletal pain significantly diminished, and the patient regained the ability to move.

Tumor enucleation was conducted, and the pathological examination of the maxillary sinus lesion unveiled a central Giant cell granuloma. The patient had clinical and laboratory improvement after surgery. This finding confirmed our diagnosis of a paraneoplastic hypophosphatemia associated with a giant cell granuloma.