Journal of Research in Medical Sciences1735-199516820110815Unusual presentation in a case of primary hyperparathyroidism74747474ENLorenaAiraghiMedicina Interna 1B, Fondazione IRCCS Cà Granda, Ospedale Maggiore Policlinico, Milano. lorena.airaghi@policlinico.mi.itGiuseppinaPisanoEdoardoPulixiRiccardoBentiMarinaBaldini201107202011081220110811This report describes a case of classic severe primary hyperparathyroidism (PH) with clinical presentation that is very infrequent nowadays, which was osteitis fibrosa cystica. As bone scintigraphy demonstrated multiple areas of increasing uptake associated with hypercalcemia, a thorough investigation was conducted to exclude the neoplasms which most frequently are responsible for bone secondarisms. A fludeoxyglucose (FDG) positron emission tomography/CT demonstrated diffuse and multiple foci of increased FDG uptake and a focal uptake at the left thyroid region. Parathyroid function was studied, revealing unexpectedly high parathyroid hormone (PTH) levels. Further tests confirmed the diagnosis of PH and localized a parathyroid adenoma in the lower left side.KEYWORDS: Primary Hyperparathyroidism, Osteolysis, Neoplastic Hypercalcemia, Bone Scintigraphy, Bone Secondarisms, Parathyroid Adenoma