Endocrine Abstracts

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused by the abnormal production of fibroblast growth factor 23 (FGF23) in the tumor. Here we report a case of TIO with pulmonary adenocarcinoma. A 61-year old woman was referred to our hospital. She was suffering from severe polyarthralgia and bilateral limb weakness. Her blood chemistry revealed high alkaline phosphatase, low phosphate, low calcium, and low 1,25-(OH)₂D₃. Bone-scintigraphy revealed multiple accumulations in femoral neck, sacrum, 1st rib, sacroiliac joints and many other joints, suggesting small fractures and systemic arthritis. Endocrinological analyses exhibited elevated iPTH and markedly high FGF23 level of 3900 pg/ml (reference: 14.7–40.5 pg/ml). These findings suggest that the FGF23-producing tumor of uncertain location induced osteomalacia in this patient. DOTATOC-PET/CT showed a major uptake in a nodular lesion of the left lung and several minor uptakes in the supraclavicular, hilar and mediastinal lymph nodes. An ultrasound-guided fine needle aspiration biopsy of the left supraclavicular lymph node was performed and the histological diagnosis was metastatic adenocarcinoma. PNA-LNA PCR clamp analysis of the biopsy specimen detected a mutation in Exon19 of the EGFR gene. She was diagnosed as stage IVA (cT1cN3M1b) pulmonary adenocarcinoma, and the chemotherapy with afatinib maleate (EGFR tyrosine kinase blocker) was started. At the same time, alfacalcidol was prescribed for osteomalacia. After 5 months, the primary tumor and metastatic lesions are gradually shrinking. The bone metabolism is almost normalized, and FGF23 level is markedly decreased (42 pg/ml). At present, the arthralgia is ameliorated and controlled with minimal dose of analgesics. This is a rare case of TIO associated with pulmonary adenocarcinoma. The DOTATOC-PET/CT was an effective modality for diagnosis.