Primary hyperparathyroidism and benign monoclonal gammopathy.

Three patients had primary hyperparathyroidism and monoclonal serum immunoglobulins. Although multiple myeloma was suspected in each case, subsequent evaluation was consistent with a "benign monoclonal gammopathy". Parathyroid adenomas were removed from two patients. The three patients are presented and compared to the four other cases that have been reported previously. The association between primary hyperparathyroidism and benign monoclonal gammopathy is discussed in terms of possible pathogenetic mechanisms. Primary hyperparathyroidism should be suspected in patients with hypercalcemia and benigh monoclonal gammopathy, as well as in other conditions, like multiple myeloma, that are known to be associated with hypercalcemia.