“D” is for Dilemma

Immunoglobulin D (IgD) monoclonal gammopathy is a rare subtype of multiple myeloma (MM) associated with a worse prognosis compared with other variants of MM. A 61-year-old man with no known past medical history presented with complaints of abdominal pain, nausea, and vomiting for three weeks. Physical examination revealed mild epigastric tenderness. Laboratory data demonstrated a significantly elevated creatinine with minimal proteinuria and small abnormality in the gamma fraction. Ultrasound of the kidneys described normal-sized kidneys. Serum-free light chains and immunofixation were consistent with IgD kappa monoclonal gammopathy. Kidney biopsy revealed cast nephropathy. Bone marrow biopsy was remarkable for sheets of CD 38+ plasma cells comprising approximately 80% of the marrow cells. Recognizing the atypical presentation of IgD MM is crucial to facilitate early diagnosis and management and improve the prognosis of this subtype of MM.