The spectrum of renal disease associated with microscopic polyangiitis and classic polyarteritis nodosa in Kuwait

Background. This study was conducted to examine prospectively the epidemiological profile of renal disease associated with microscopic polyangiitis (MPA) and classic polyarteritis nodosa (classic PAN) in Kuwait and its clinicopathological correlation. Methods. Between 1 January 1993 and 31 December 1996, all patients referred to Al-Amiri renal centre were subjected to renal biopsy and/or arteriography if they manifested systemic manifestations of vasculitis or had rapid or unexplained renal failure with or without proteinuria. Patients who fulfilled the criteria of MPA and classic PAN, according to the Chapel Hill Consensus Conference (CHCC), were included in the study. Results. Over those 4 years, 47 patients were diagnosed as having such vasculitides, 22 of whom were Kuwaiti nationals. This gave an average annual incidence of 45 cases/million adult Kuwaiti nationals (95% CI, 27-64). Histological examination revealed necrotizing glomerulonephritis (GN) in 11 patients and crescentic GN in 13, while isolated small- and/or medium-sized-arteritis were evident in six more patients. In 10 of the remaining patients, bands of fibrosis alternating with healthy renal tissue were seen and on arteriography non-atherosclerotic stenoses, infarctions, and/or microaneurysms were evident. The remaining seven patients were diagnosed by arteriography alone, five of whom had bilateral small kidneys. Constitutional manifestations of vasculitis were present in 32 patients (68%) and multisystem involvement in 19 (40%). ANCA levels were high in 24 (55%) of the 44 patients tested and seropositivity, as an antimyeloperoxidase, was a constant finding. Only six patients presented with rapidly progressive renal failure, while 31 presented with chronic renal disease, 18 of whom had protein excretion in excess of 2 g/day. Conclusions. These findings emphasize the limited role of clinical assessment in establishing a definite diagnosis of renal vasculitis and put in question its value in retrospective analysis of causes of ESRD in different populations.