MYELOMA IN A HYPERCALCEMIC PATIENT. S. Chebrolu 1 , F. Zar 1 ; 1 St. Francis Hospital, Evanston, IL LEARNING OBJECTIVES: 1) Recognize that Primary Hyperparathyroidism (PHP) and Multiple Myeloma (MM) are the most common causes of hypercalcemia in the elderly population and diagnose them. 2) Recognize that more than one independent cause of hypercalcemia is very rare and should be considered in a patient unresponsive to treatment. CASE INFORMATION: A 76 year-old male was admitted with weakness, lethargy and occasional confusion of three months duration. His past medical history included sick sinus syndrome and valve replacement for aortic incompetence. His primary doctor discontinued chlorthalidone four weeks prior to this admission after he was found to be hypercalcemic (13.9mg/dl). Examination was unremarkable. Initial studies revealed calcium 11.8mg/dl (normal 8.8±10.4mg/dl), ionized calcium 6.77 mg/dl (normal 4.6±5.3mg/dl), and phosphorus 2.3 mg/dl (normal 2.4±4.5mg/dl). CT scan of head was normal. Patient was hydrated with normal saline and later diuresed with furosemide. An intact parathyroid hormone level by immunochemiluminescent assay was 12.1 pmol/l. C-terminal peptide was 323 pmol/l. Serum osteocalcin was 21U/l. A CT scan of the neck showed a mass suggestive of a parathyroid adenoma, confirmed by Technetium-99m sestamibi scan showing a persistent crescentric area of increased activity in the left lower neck in both immediate and delayed films. In addition, urine protein electrophoresis showed monoclonal kappa light chains. Serum protein electrophoresis revealed a monoclonal spike and IgG kappa monoclonal protein (2770mg/dl). Beta-2 microglobulin was 6.4mg/dl. A skeletal survey revealed multiple lytic defects throughout the skeletal system. Bone marrow aspiration showed focal increase in plasma cells consistent with MM. The patient was given pamidronate and started on chemotherapy with melphalan and he responded well. DISCUSSION: Although a variety of conditions can give rise to hypercalcemia, nearly 90% of the cases can be attributed to either PHP or MM. PHP was diagnosed in our patient by finding elevated intact parathyroid hormone levels associated with elevated C-terminal peptide levels. Technetium-99m-sestamibi scan confirmed its presence. IgG kappa monoclonal paraprotein on serum and urinary protein electrophoresis associated with multiple lytic defects on the skeletal survey was highly suggestive of MM which was confirmed by bone marrow biopsy. However, more than one independent cause of hypercalcemia in a patient is rarely seen. Only eighteen cases of simultaneous occurrence of both PHP and MM were reported and our patient will be the nineteenth such case. Considering the rarity, it appears that this is a chance association. Persistent and unresponsive hypercalcemia may occur if only one of causes is recognized in such rare instances and in a MM patient, this may falsely lead to a higher tumor grading.