Osteitis Fibrosa Cystica A Rare Presentation of Primary Hyperparathyroidism

Introduction: Osteitis fibrosa cystica (OFC) is the most serious bone involvement of primary hyperparathyroidism (PHPT), it is characterized by subperiosteal resorption, lytic lesions and the appearance of brown tumors; this is why, in some cases, this condition can easily be mistaken for a malignant neoplasm. Its prevalence in developed countries is only 5%. Clinical Case: We present a 58-year-old woman, with no relevant personal history, who came to the emergency room with pain in her right shoulder after an accidental fall on the bus. The humerus radiograph shows a pathological fracture of the right humerus, with significant osteopenia. In the emergency analysis, serum Calcium 13.3 mg / d), Ionic Calcium 7.03 mg / dL, Phosphorus 2.4 mg / dL, Alkaline Phosphatase 248 U / L and normal kidney function stand out. With a diagnosis of severe hypercalcemia, treatment was started in the emergency room with serum therapy (1000 ml of 0.9% physiological saline in 4 hours) and intravenous diuretic treatment (furosemide 40mg) with a decrease in calcemia to 12.8mg / dL. Later, she was admitted to the Internal Medicine hospital ward to perform a differential diagnosis of hypercalcemia secondary to a primary tumor, Multiple Myeloma or Primary Hyperparathyroidism. The study findings are: Calcium metabolism: PTH 660 pg / ml (12 - 65), 25 Hydroxyvitamin D: 14.00. Thyroid ultrasound: Posterocaudal to right thyroid lobe, an area of ​​echogenicity slightly lower than the thyroid is identified, of dimensions not estimated by endothoracic component, which could correspond to a parathyroid adenoma. Body CT: Neck: Heterogeneous nodule dependent on the posterior region of the right thyroid nodule with endothoracic extension. Skeleton: Lytic lesions with a tumor aspect in the humerus, right scapula and bilateral seventh rib and right pubic branch. Skull: Diffuse increase in bone density of the calvaria, showing multiple punctate lytic lesions with a permeative appearance. Bone densitometry: Femur neck: - <1.5, Lumbar spine: - <3.0 With the diagnosis of PHPT causing osteitis fibrosa cystica, surgical intervention was decided. Under general anesthesia, a selective right approach was performed, finding a large parathyroid adenoma weighing 17 grams. PTH fell to 36 pg / ml after surgery. At 9 months after surgery, the patient presented calcium levels of 9 mg / dl and PTH 146 pg / ml with clear radiological improvement. Discussion: Osteitis fibrosa cystica is rare in our environment, it is often confused with other neoplasms. After parathyroidectomy, patients with PHPT have a marked and sustained recovery from OFC, although in some cases this recovery can only be achieved after several years. We consider this case of interest, since it illustrates the importance of evaluating the study of phospho-calcium metabolism and parathyroid function in all patients with bone lesions to rule out Primary Hyperparathyroidism with OFC.