Paget's Disease of Bone and Normocalcemic Variant of Primary Hyperparathyroidism in an Osteoporotic Male: Exceptional Coexistence.

Background and clinical significance: Paget's disease of bone involves anomalies of the bone metabolism; however, the presence of tumor-derivate abnormal parathyroid hormone (PTH) levels does not represent one of these disturbances. To our best knowledge, the association with normocalcemic variant of primary hyperparathyroidism has been limitedly reported, and here we introduce such an unusual overlap in a male suffering from osteoporosis. Case presentation: A 71-year-old, non-smoker man was hospitalized for mild, nonspecific dysphagia, asthenia, decreased appetite, and mild weight loss during the latest 2 months. His medical history included cardiovascular conditions and an abnormal PTH level with normal serum calcium under daily cholecalciferol supplements (tested twice during latest 12 months). The lab findings pointed out a normocalcemic primary hyperparathyroidism (PTH of maximum 163 pg/mL, and total calcium of 9.3 mg/dL) caused by a right parathyroid tumor of 1.2 cm, as confirmed by computed tomography (CT). Additionally, CT showed a left humerus lesion suggestive of Paget's disease of bone, a confirmation that also came from the whole-body bone scintigraphy. The subject presented increased P1NP and osteocalcin, CrossLaps as bone formation, and resorption markers, with normal total alkaline phosphatase. CT scan also detected multiple vertebral fractures and small kidney stones. Zoledronate i.v. (3 mg, adjusted for creatinine clearance) was administered, taking into consideration all three bone ailments (Paget's disease, high PTH/calcium, and osteoporosis) with further follow-up. Conclusions: This case highlights the following technical notes based on a real-life setting: 1. Despite the mentioned bone diseases, no bone pain was present. Loss of appetite, dysphagia, and asthenia may be a consequence of mineral metabolism disturbances. 2. The panel of blood bone turnover markers levels might be related to both hyperparathyroidism and Paget's disease; notably, rare cases of Paget's disease with normal alkaline phosphatase were prior reported. 3. A meticulous differentiation between secondary and primary hyperparathyroidism is required. In this instance, lack of hypocalcaemia and vitamin D deficiency was suggestive of the diagnosis of a primary variant. 4. Kidney stones, osteoporosis, and osteoporotic fractures may be correlated with both conditions, as well, while a dual perspective of the therapy, since the patient was not a parathyroid surgery candidate, included a first dose of zoledronate with consecutive long-term follow-up. To our best knowledge, the co-presence of normocalcemic variant of primary hyperparathyroidism represents an exceptional finding in a patient synchronously diagnosed with Pagetic lesions and osteoporosis complicated with vertebral fractures.