OP17. PATHOLOGIC FEATURES OF TAKAYASU'S ARTERITIS (NON SPECIFIC AORTOARTERITIS)

Abstract

Takayasu's arteritis or Non-specific aortoarteritis (NSAA) is an uncommon form of large vessel vasculitis and has been known by various names. The morbid anatomical features of NSAA described here are based on the autopsy findings of 80 cases seen in a 30-year period. These autopsies were carried out at Seth GS Medical College & KEM hospital, Mumbai. With an active autopsy service, the incidence of NSAA is about 0.15%. 46.25% of these cases were in the pediatric age group. In the aorta the disease had 2 patterns of involvement: (a) Segmental lesions either single or multiple, with skip areas in between. (b) Diffuse extensive disease. Marked periadventitial and adventitial fibrous thickening with adhesions to neighboring structures with enlarged lymph nodes is often noted around the involved segments. The aorta is stiff and rigid, sometimes with dilated segments and aneurysms. Localised stenotic lesions is fairly common (37.5%), seen particularly in children and is noted in the descending thoracic (DTA) and abdominal aorta. In our material the DTA is the segment maximally affected. The lesion starts at the level of L subclavian or just beyond it to involve variable lengths of DTA. Abdominal aorta (renal artery segment) disease is more common in adults. This is often associated with renal artery stenosis. In diffuse disease the thoracic abdominal aorta is affected, sparing the ascending aorta. In autopsy material, isolated arch vessel disease is rare. When arch vessel is diseased, it involves mainly the L Subclavian and there is always associated aortic arch disease. Arch vessel disease is in the form of complete block or osteal narrowing with occlusive luminal thrombi. Coronary osteal stenosis is not uncommon. The intimal surface of the aorta is covered with gelatinous or whitish plaques or is diffusely thickened. Mural thrombi are sometimes present in the constricted segment. Histopathological features: Inflammation may be in the active or more commonly in the chronic healed phase. In the active phase, diffuse or granulomatous inflammation is seen consisting of Langhans giant cells, foreign body giant cells, mixed inflammatory cells and sometimes-fibrinoid necrosis. Inflammatory reaction is maximal at the junction of the media and adventitia and is marked around vasavasorum though there is no vasculitis. Adventitia shows increase in ground substance with acid mucopolysaccharides. Media shows neovascularization and inflammatory cells. Intima is thickened with increase in ground substance. There is no intimitis. In chronic phase there is sparse inflammation around vasavasorum, adventitial thickening, fibrosis, scarring in the media, disruption of elastic fibres and hyaline intimal thickening. Pulmonary artery and coronary artery involvement is infrequent. The commonest associated pathology noted at autopsy is tuberculous lymphadenitis (55%). Matted enlarged Para aortic and mediastinal lymph nodes are particularly present around the involved segments of aorta. It is not easy to reconstruct the natural course of the disease. Symptoms are related to well establish lesions in the aorta or its branches. The inflammatory process may be self limiting in most cases. Regression of lesions has been documented in a few case reports. Prognosis is influenced by clinical course, age of onset and complications like hypertension, rapid development of congestive cardiac failure, and left ventricular failure. As of today there is no specific disease activity marker and treatment should be aimed at preventing vital organ ischemia and cardiac failure.