The differential diagnosis involves the consideration of all other causes of hypercalcaemia. In patients who are normo-calcaemic but present with recurrent renal stones, other causes of recurrent renal stones (such as idiopathic hypercalciuria, oxaluria, urate stones or cystinuria) should be considered. In patients who present with osteopenia, osteoporosis, osteomalacia and malignant disease (most notably myeloma) should be excluded.
