In 1993, a 73-year-old man was admitted to the internal medicine department with a provisional diagnosis of bone metastasis from an unknown primary tumour. He had lost 15 kg in 18 months and manifested anorexia, constipation, left thigh pain and elevated blood concentrations of calcium, bilirubin, acid and alkaline phosphatases. Bone scan demonstrated multiple areas of increased uptake and hypertrophic osteoarthropathy, suggesting metastatic disease.

The patient's personal history was unremarkable, except for having undergone surgery for a maxillary tumour at the age of 18 (1938). Histological diagnosis of this tumour was not available.
During admission, elevated urinary parathormone and blood calcium levels were found. Cervical ultrasonography showed enlargement of the right lower parathyroid gland.
The patient underwent right hemithyroidectomy with excision of the enlarged parathyroid and ipsilateral gland; calcaemia was immediately normalised. Histopathology showed infiltrating carcinoma of the lower parathyroid and hyperplasia of the upper parathyroid.
Two years later, bone pain and constipation with elevated blood levels of calcium and parathormone occurred again. In a new operation, a haemithyroidectomy, left parathyroidectomy and thymectomy were performed. Calcaemia normalised but the patient died two years later of unrelated causes.
