In June 2018, 77-year-old man was referred to The Department of Haematooncology, University Hospital Ostrava, for suspicion of multiple myeloma. This was supported by laboratory findings of hypercalcemia, paraprotein IgA κ in serum and by the presence of multiple osteolytic skeletal lesions. Low number of plasma cells in bone marrow sample - cytologically (3.6 %) as well as in flow cytometry (less than 95 % clonal plasma cells out of total bone marrow plasma cells) - pointed at the direction of monoclonal gammopathy of undetermined significance (MGUS). In the course of differential diagnosis of hypercalcemia, elevated level of parathormone had been found which led to the performance of 99mTc-MIBI scintigraphy where parathyroid adenoma was discovered and later histologically verified. The final diagnosis was determined as a coincidence of MGUS and primary hyperparathyroidism. This case report also contains brief differential diagnosis of hypercalcemia and osteolytic skeletal lesions and suggestions for their diagnostic algorithms.
Keywords: MGUS; hypercalcemia; multiple myeloma; osteolytic lesions; primary hyperparathyroidism.