Morphometric analysis of the kidney lesions in mixed connective tissue disease (MCTD)

We examined histopathological changes of the kidney in patients with mixed connective tissue disease (MCTD) including those of glomeruli, arteries and interstitium by morphometric method. All specimens examined were collected from 25 autopsy cases diagnosed as MCTD according to the criteria for this disease proposed by the MCTD committee sponsored by the Japanese government. Clinical evidence of renal dysfunction such as proteinuria was present in 16 out of 25 cases (64%). Histopathologically, membranous type glomerular lesion was found most frequently (40%), followed by membrano-proliferative (6.7%) and mesangioproliferative types (6.7%). Nine cases had no glomerular lesion. Severe arterial lesion such as necrotizing angiitis was not found in our kidney specimens. However, morphometry revealed a high incidence of intimal thickening in the renal arteries of these patients as compared to control cases, showing this to be one of the most common features of MCTD with clinical importance. This type of arterial lesion, also seen in kidneys in other types of collagen diseases, may suggest an etiology common to them. The severity of the renal interstitial lesion in MCTD was intermediate between that of systemic lupus erythematosus (SLE) and progressive systemic sclerosis (PSS), poly-or dermatomyositis (PM/DM).