Endocrine Abstracts

Introduction: Oncogenic Osteomalacia (OO) is a rare paraneoplastic syndrome, resulting from fibroblast growth factor 23 overproduction. The rarity of the disease and nonspecific symptoms often cause delay in diagnosis by months, or even years. There are two cornerstones in the diagnostic process. The first concerns clinical identification, where awareness of this uncommon ailment combined with hypophosphatemia and clinical signs may be sufficient to identify OO. The second involves imaging procedures to anatomic localisation of the tumor, which can be complicated as the lesions are usually small, and may occur at various sites.

Aim: We present a case of OO where the whole diagnostic process and treatment took one week, in a patient misdiagnosed during the previous three years. We would like to emphasise that such a fast diagnosis is possible without sophisticated imaging tools. Awareness of this rare disease, coupled with conscientious physical examination can be enough for diagnosis, resulting in efficient treatment.

Materials and methods: Day 1. Physical examination and clinical features:

Patient’s main complaints included severe bone pain, general fatigue, muscle weakness, as she required walking assistance. Upon physical examination she exhibited a waddling gait, had pain on palpation of the bones and joints; a flat, cohesive lesion in the subcutaneous tissue in the region of the right scapula was notable.

Day 2. Laboratory diagnosis: Mild hypophosphatemia and increased activity of alkaline phosphatase were documented (FGF-23 and 1,25(OH)2D3 in process).

Day 3. Imaging diagnosis and surgery Soft tissue US of the right scapula region revealed subcutaneous tissue 21x6x27mm, with heterogeneous decreased echogenicity, smooth contours, and increased vascularity.

Surgical removal of the lesion in the right scapula region was performed.

Day 4. Observation: Neither clinical nor biochemical improvement was noticed.

Day 5. Discharge from the hospital: MR of the whole body was planned as part of out-patient diagnosis continuation.

Day 7. Histopathological result: Phosphaturic mesenchymal tumour with small fusiform cells, which focally undergo chondroblastic-like differentiation.

Gradually, phosphate increase and alkaline phosphatase decrease were observed; subsequently the patient began to walk without aid, the waddling gait ceased, general fatigue and pain ended.

Conclusion: By presenting this case we would like to remind clinicians about OO as a rare cause of hypophosphatemia. Prompt diagnosis and treatment can prevent a patient from becoming disabled. Based on our experience, we assume that removing easily accessible lesions before performing sophisticated imaging studies for its localization should be recommended.