[Ecchymotic angioedema revealing childhood systemic lupus erythematosus with anti-C1q antibodies].

BACKGROUND: Hypocomplement urticarial vasculitis syndrome may be the presenting sign of systemic lupus erythematosus. Hypocomplement urticarial vasculitis presents as atypical urticaria associated in 50% of cases with angioedema. On laboratory investigation, hypocomplementaemia is the characteristic feature, with reduced C3, C4 and C1q. This disease is very rare in children.

PATIENTS AND METHODS: An eight-year-old girl was hospitalised for relapsing urticaria with ecchymotic angioedema present for one year, in a setting of impaired general health and fever. Screening for native anti-DNA and antinuclear antibodies was positive. Analysis of complement revealed activation of the classical pathway with reduced CH50, C4 and C3. These anomalies persisted outside active episodes. The C1q fraction was completely depressed and screening for anti-C1q was positive. There was no quantitative or qualitative deficit in C1-esterase inhibitor. Direct immunofluorescence of skin lesions demonstrated deposits of immunoglobulin and complement. These episodes of angioedema persisted despite long-term systemic corticosteroid therapy (1mg/kg per day).

DISCUSSION: This is the first reported case of hypocomplement urticarial vasculitis syndrome arising from systemic lupus erythematosus in a child exhibiting anti-C1q antibodies. Furthermore, this case is original because of the highly ecchymotic nature of the lesions. In the presence of angioedema with ecchymotic progression associated with atypical chronic urticaria, a diagnosis of hypocomplement urticarial vasculitis syndrome should be considered.