What is urticarial vasculitis (UV)?
UV is an SVV presenting with urticarial lesions instead of the more typical palpable purpura. Because of this unusual presentation, UV was separated from the other types of necrotizing SVV. UV can be divided into two groups:
- • Normocomplementemic UV is a self-limited subset of hypersensitivity vasculitis. It is usually idiopathic.
- • Hypocomplementemic UV (HUV).
HUV can be seen in isolation (75% of cases) or associated with an underlying autoimmune disease (25% of cases; primarily systemic lupus erythematosus [SLE] and to a lesser extent Sjögren’s syndrome). As such, in patients presenting with HUV, screening for an underlying autoimmune disease is recommended. HUV is commonly associated with systemic symptoms (70%–80% of cases) and is called HUV syndrome (HUVS). Schwartz et al. defined this as HUV + 2 minor criteria (LCV, arthralgia/arthritis, ocular inflammation, glomerulonephritis, abdominal pain, and/or anti-C1q antibody). Common systemic features (in addition to chronic urticaria) include arthralgia (80%), scleritis/uveitis/episcleritis (50%), angioedema (50%), obstructive pulmonary disease (20%), glomerulonephritis (15%), as well as GI (20%) and cardiovascular disease (<5%). Some authors include anti-C1q antibody (C1q precipitins) positivity as a requirement in HUVS, but registries using the Schwartz criteria have placed the sensitivity of this antibody around 60% in cohorts with HUVS. Low C1q levels are present in >90% of patients, however, suggesting it may be a more sensitive marker for disease.
