Idiopathic polyarteritis nodosa - does it still exist? Viewpoint 1: as our knowledge makes progress, idiopathic polyarteritis nodosa is fading away.

Polyarteritis nodosa (PAN) was first described in 1852 with the first widely recognised description in 1866 by Kussmaul and Meier. Since then our concepts of the condition have evolved, with recognition of the difference between polyarteritis nodosa and microscopic polyangiitis (MPA). Classification criteria for PAN remain unsatisfactory. The ACR criteria from 1990 did not recognise MPA or ANCA, with the result that their sensitivity and specificity are poor. The modern ACR/EULAR criteria as yet do not include PAN as yet. The aetiology is better understood, with recognition that hepatitis B associated PAN is a separate condition, discovery of genetic syndromes including DADA2 and VEXAS which can mimic PAN. Epidemiology suggests that PAN is becoming increasingly rare. Truly idiopathic PAN will gradually become a much rarer condition and may well disappear completely.