Extramedullary haemopoiesis in the small bowel.

A patient with myelofibrosis developed repeated gastrointestinal haemorrhage from the small intestine, which was found to be infiltrated with extramedullary haemopoiesis. Nineteen months later he presented with subacute intestinal obstruction; radiology and laparotomy documented progressive infiltration of the small bowel. Histological examination of the resected terminal ileum showed patchy mucosal ulceration, with underlying submucosal and serosal extramedullary haemopoiesis.