Functional asplenia in malignant mastocytosis.

A 47-yr-old man with malignant mastocytosis, a malignant neoplasia of mast cells, presented with anemia. Ultrasonography revealed an enlarged spleen. A liver-spleen scan using [99mTc]sulfur colloid failed to show any splenic uptake consistent with the diagnosis of functional asplenia. Functional asplenia related to this condition has not been reported previously. Since the spleen was heavily infiltrated with space occupying mast cells, a mass displacing effect along with impaired perfusion are discussed as underlying mechanism.