Natural Killer Cell Enteropathy With Extraintestinal Involvement: Presenting as Symptomatic Anemia

Natural killer (NK) cell enteropathy is a newly described disease entity with benign behavior and an indolent clinical course, characterized by the atypical proliferation of NK cells throughout the gastrointestinal tract. The exact etiology is unknown. It closely mimics NK/T-cell lymphoma. We describe this atypical entity in a young adult man presenting with vague upper gastrointestinal symptoms and anemia requiring blood transfusion. The response to budesonide therapy points toward a possible low-grade autoimmune process. Considering the benign behavior and self-limiting course, recognizing this entity is essential to avoid over the investigation and aggressive, inappropriate therapy.