The case of a 67-year-old man presenting with parathyroid gland adenoma associated with multiple organ manifestations of a rare normocalcemic form of primary hyperparathyroidism is described. The authors draw attention to the importance of correlating clinical and laboratory examinations with histological, radiological and scintigraphic findings for the establishment of diagnosis. They emphasize the role of two-phase 99mTC-MIBI (methoxyisobutyl-isonitril) scintigraphy not only for diagnostic purposes but also for exact localization of the adenoma by means of a gamma probe during surgery. They also point out the possibility of accompanying pathological conditions, in this case, the development of a tumor described as "brown tumor". This was shown by angiography as a hypervascularized and strongly stained expanding lesion. The authors conclude that the early surgical removal of this parathyroid gland adenoma was important for the patient's successful recovery.