Sarcoidosis and Monoclonal Gammopathy of Undetermined Significance (MGUS): A True Association or Just a Coincidence?

Sarcoidosis is a systemic inflammatory disease characterized by the presence of noncaseating granulomas in different organs. Sarcoidosis associated with monoclonal gammopathy of undetermined significance (MGUS) is a rare finding with only 10 cases reported to date. We describe a 79-year-old male patient who presented with dry mouth for 4 months. Lip biopsy done prior to admission showed nonnecrotizing epithelioid cell granulomas. On admission, laboratory analysis was significant for elevated calcium, decreased parathyroid hormone, increased erythrocyte sedimentation rate, undetectable parathyroid hormone-related peptide (PTHrp), mildly decreased 25-hydroxyvitamin D, elevated 1,25-dihydroxyvitamin D, elevated angiotensin converting enzyme, and positive Bence Jones protein in the urine. Serum protein electrophoresis showed an elevated gamma globulin level at 38% and an IgG monoclonal gammopathy with an M-spike of 1.47. Bone marrow biopsy was consistent with MGUS. The patient showed significant improvement with steroids and was discharged with close follow-up from nephrology and oncology. Salivary gland involvement in patients with sarcoidosis is a rare finding. Our case is a valuable addition to the small number of cases described in the literature supporting an association between plasma cell disorders and sarcoidosis. Larger prospective studies are needed to determine if a true association between the two diseases exists.