New histologic findings in idiopathic mesenteric phlebosclerosis: clues to its pathogenesis and etiology--probably ingested toxic agent-related.

BACKGROUND Idiopathic mesenteric phlebosclerosis (IMP) is a recently known and rare disease entity, which is a member of non-thrombotic, non-inflammatory stenosis or occlusion of the mesenteric veins. In spite of the unique histopathology and particular location, the cause and pathogenesis of IMP remain unknown. The aim of this brief study was to propose a pathogenesis and possible etiology based on the reviewed clinical data and some newly discovered pathologic findings in several recent cases in our and other hospitals. METHODS The clinical data of 5 patients were collected, with detailed tracing of past history, drug use and dietary habit. The histologic sections were reviewed in detail, with additional histochemical stains and immunohistochemical stains in 4 available cases. RESULTS The most important of our findings other than the previously described typical features was a unique type of coagulative necrosis, which we call mummification, involving not only the muscular coat of veins in early and late phases but also the subsequent hyperplastic myointima in veins, portion of the media of arteries closely neighboring the sclerotic vein, a zone of muscular wall of the colon around the passing sclerotic veins and the inner zone of muscular wall of the colon, and accompanied by fibrosis/sclerosis and then calcification in the damaged tissues. Two of our patients were a couple who had been taking Chinese herbs regularly. CONCLUSION A pathogenesis is suggested for at least a subgroup of cases of IMP: the disease is initiated by a slow but longstanding direct hypoxic injury to the venous muscular layer, which leads to gradual mummification and then sclerosis and calcification of the venous muscle. This is followed by the repeated same damage of the subsequent reactively hyperplastic myointima in the veins, and these changes finally result in gradual venous occlusion. Certain toxins or biochemicals, probably existing in the frequently ingested contents and absorbed to the venous return, may play the most important role in this damage. However, analysis of more cases is required to support the proposal, and if such support is found, the toxic agents remain to be clarified via further laboratory investigations.