A Tale of Two Immunodeficiencies: A Case of Multiple Myeloma Associated with Profound Immune Defect Mimicking Common Variable Immunodeficiency Syndrome.

INTRODUCTION: Multiple myeloma (MM) is a clonal plasma cell disorder commonly associated with secondary immune deficiency. By contrast, common variable immunodeficiency (CVID) is a primary immunodeficiency characterized by low serum levels of immunoglobulins (IgG, IgA, and/or IgM) and inability to produce specific protective antibodies in response to infections and immunizations. Besides a defective immune system and susceptibility to infections, CVID is associated with autoimmune disorders, gastrointestinal tract inflammation, granulomatous disease, and malignancies. Although MM and CVID both manifest an abnormal immune system homeostasis, the pathogenesis of the immune defect is distinctly different: Quantitative deficiency of the normal plasma cells in the former and qualitative defect in plasma cell maturation in the latter. CASE PRESENTATION: An unusual case of MM associated with profound immunodeficiency mimicking CVID occurred in a 51-year-old man with a history of numerous bacterial infections and low γ-globulin levels. DISCUSSION: A hypothetical connection between MM and CVID is discussed. Patients with MM who have an unusually high burden of infections and profound immune deficit persisting even after successful myeloma therapy merit recognition as a distinct cohort that warrants heightened attention from clinicians and scientists.