HSN in adults is a serious relapsing disease, causing renal failure as frequently as in small-vessel ANCA-positive vasculitides. Prognosis and risks differed in this series from those in other countries, including a higher risk of ESRF than in previous series. Distinct groups developed either ESRF, or remitted. The absence of clear benefit suggests that corticosteroids should be reserved for patients with serious disease, and that cytotoxics may not be merited for those at high risk of renal failure.

Similarities between SVD PACNS and microscopic polyarteritis suggest the former may represent a limited form of the latter. MVD PACNS has a distinctly more benign relapse pattern than its multisystem counterpart polyarteritis nodosa. Acute-phase serology was useful in designating inflammatory processes at presentation of patients presenting with encephalopathy caused by SVD only, but were unhelpful in defining relapses in this form of PACNS, the definition of which in all cases rested on clinical assessment and MR scanning. Direct cerebral angiography was not diagnostic in any case of SVD PACNS; positive brain biopsy is diagnostically unequivocal, but the total clinical syndrome with imaging may establish a diagnosis with highest probability. In MVD PACNS, angiography with MR scan proved diagnostic. We suggest an algorithm for a rational, minimally invasive approach to investigation. In PACNS, SVD and MVD are important variants, and decisions about therapy should incorporate these distinctions.

No abstract