Prognosis

The prognosis of PAN is improving because of earlier detection and more effective treatment. The 5-year survival of patients diagnosed between 1963 and 1995 was 76.5% compared with 87.9% in those diagnosed after 1995 in one study.[102] In PAN unrelated to hepatitis B virus (HBV) infection, the 5-year survival rate is 83.4%, compared with a 5-year survival rate of 73.4% in HBV-related PAN.[102] This is similar to the rates in vasculitis associated with antineutrophil cytoplasmic antibodies.[55]

The relapse rate in HBV-related PAN is <11%, lower than that in non HBV-related PAN (19.4% to 57%).[20][55][102]​​[103]​​ However, the mean time to relapse is 29 months in both groups.[102] A time to diagnosis of more than 90 days is related to an increased risk of future relapse, but is not associated with increased mortality.[104]

When triple therapy with corticosteroids, antivirals, and plasma exchange is used in patients with HBV-related PAN, seroconversion from HBeAg to HBeAb is achieved in 49.3% of patients; those who seroconvert usually achieve complete remission with no relapses.[20]

Prognostic factors

The 5-factor score predicts survival in PAN.[19] The score consists of the following factors:

  • Proteinuria >1 g/day

  • Serum creatinine >140 micromol/L (>1.58 mg/dL)

  • Cardiomyopathy

  • Gastrointestinal (GI) symptoms

  • Central nervous system (CNS) involvement.

Each item is scored one point if present. At 6 years in one prospective study, 86.1% of those with a score of 0 were alive, 69.4% with a score of one were alive, and 47% with a score of two or more were alive.[19]

Mortality can also be predicted by using the Birmingham Vasculitis Score, which is a clinical index of disease activity.​[19][55][105]​ Although included in the 5-factor prognostic score, cardiomyopathy and CNS involvement are not independent predictors of mortality.[19]

GI involvement

GI involvement, specifically GI bleeding, perforation, infarction, and/or pancreatitis (but not cholecystitis), is an independent risk factor for higher mortality, especially during the acute phase.[19][54][106][107][108][109]

A retrospective review of 24 patients with PAN and abdominal involvement illustrated this: three of 13 patients with an acute abdomen died, compared with one of 11 patients with other GI symptoms.[35] This compared favourably with a similar previous study in 1982, reporting 100% mortality in patients presenting with an acute abdomen.[110] The lower mortality in the more recent study may be due to earlier diagnosis and improvements in surgical and medical therapy.[35] GI involvement is more common in patients with HBV-related PAN.[20]​[21]​​

Renal involvement

The Chapel Hill Consensus Conference (CHCC) definition was not applied in the development of the 5-factor score.[19] Consequently, the increased mortality in patients with raised creatinine and proteinuria may relate to patients with microscopic polyangiitis rather than PAN. However, a study of 10 patients with PAN (as defined by the CHCC) found that 70% had renal involvement at diagnosis, with two patients developing end-stage renal failure.[103]

Age

Older age at diagnosis is an independent predictor for death in the first year after diagnosis, and age over 50 years is associated with decreased survival at 5 years.[53][107]

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