Palpable
purpura is the hallmark of
cutaneous vasculitis. Small-vessel
vasculitis is a common
vasculitis manifestation associated with acute or
chronic infection. It is also characteristic of a systemic disease whether infectious or not. The pathogenic mechanisms appear to be
complex: immune complex formation, vessel damage or altered vessel function mediated directly by infectious agents, humoral or cellular immunologic response. It is also a reaction to mixed
cryoglobulinemia. Diagnosis of
cutaneous vasculitis is simple (palpable purpuric eruption, nodules, vesiculobullous lesions, ulcerations), but etiological investigation is often difficult because the infectious origin is only rarely demonstrated. This type of
purpura occurs in
bacterial endocarditis and therefore blood cultures must be performed in any febrile patient particularly in the presence of a
cardiac murmur. In fact the viral, parasitic or bacterial infectious origin is demonstrated in less than 30% of the cases of leucocytoclastic
vasculitis. While focal
sepsis is often found and its eradication should be followed-up, its role has not been proven particularly as
antibiotics alone themselves can cause
hypersensitivity vasculitis. Finally, mention must be made of virus induced
vasculitis (B and C
hepatitis, cytomegalovirus, parvovirus),
antiviral treatment which permits better control of
vasculitis.