An elderly man with confusion, hypercalcaemia and acute renal failure—an important diagnosis not to miss

(Section Editor: K. Kühn) The commonest causes of hypercalcaemia in an elderly man include: multiple myeloma, hyperparathyroidism, bony metastases and humoral hypercalcaemia of malignancy. Other less common causes include hyperthyroidism, sarcoidosis, vitamin D excess, Addison's disease and drugs (especially thiazide diuretics). Acute renal failure may be caused by several of the diseases listed or may be as a consequence of the hypercalcaemia itself. A 71‐year‐old Caucasian man presented via his general practitioner to the general medical outpatients with a 6‐month history of systemic symptoms. He complained of lethargy, nausea and 10 kg weight loss over the last 4 months. His wife had also noted that he was becoming increasingly confused and was suffering from short‐term memory loss. He was also currently under the urologists for prostatic symptoms with a raised prostatic specific antigen (PSA) of 31.6 μg/l (normal range <4.0 μg/l) and a malignant feeling prostate gland on rectal examination although prostatic biopsies were entirely benign. Two months earlier his creatinine was 234 μmol/l (normal range 50–110 μmol/l). He had stopped smoking over 25 years ago and occasionally drank alcohol. Physical examination revealed an elderly gentleman. His pulse rate was 60/min and blood pressure 160/100 mmHg. There were no abnormal findings other than an irregular, enlarged prostate gland. A chest X‐ray was normal. A full blood count revealed: haemoglobin 10.4 g/dl (normal range 12–16 g/dl); white cell count 5.7×10−9 (normal range 4–11×10−9/l); platelet count 309×10−9 l (normal range 150–400×10−9/l). Blood chemistry showed a normal sodium (142 mmol/l (normal range 135–145 mmol/l)) and potassium (4.5 mmol/l (normal range 3.5–5.0 mmol/l)) but a raised urea (35.6 mmol/l (normal range <8 mmol/l)) and serum creatinine (647 μmol/l). The only other abnormal result was a serum calcium concentration of 2.87 mmol/l (normal range 2.20–2.65 mmol/l).