Hypercalcaemia in systemic lupus erythematosus.

Hypercalcaemia is a common electrolyte abnormality. The vast majority of patients will be shown to have either hyperparathyroidism or malignancy. In less than 10% of patients other, less common causes of hypercalcaemia will be present. Systemic lupus erythematosus is a very rare cause of hypercalcaemia. It may be associated with lymphadenopathy and pleuritis to constitute a distinct clinical entity described as 'hypercalcaemia-lymphoedema syndrome'. In these cases the pathophysiology of the hypercalcaemia is not completely understood. In some cases it is associated with elevated levels of parathyroid-related peptide (PTHrP). In others the level of PTHrP is normal, and it has been suggested that autoantibodies may cause hypercalcaemia by activating the PTH receptor. We describe a case of a woman who presented with severe hypercalcaemia, developed the hypercalcaemia-lymphodema syndrome and fulfilled the diagnostic criteria of systemic lupus erythematosus.