Multiple Myeloma Presenting as Chronic Diarrhea.

Extramedullary gastrointestinal tract involvement in plasma cell dyscrasias is rare and represents a diagnostic challenge. We present a 66-year-old man with an unusual presentation of multiple myeloma. He presented with chronic diarrhea, and extensive biopsies in the jejunum allowed for the presumptive diagnosis of multiple myeloma to be made and the weighted decision to treat without a definitive diagnosis. Plasma cell dyscrasias can have highly varied presentations, unclear differentiation, and require a multidisciplinary approach for diagnosis and management. Adequate tissue sampling of the small bowel is critical in assessing patients with chronic diarrhea.