Skin Disorders Guide

Diagnostic Hallmarks

1. Distribution: marked predilection for the lower legs
2. Nonblanchable petechiae
3. Slightly palpable petechiae
4. Absence of ecchymoses

Clinical Presentation

The purpuric lesions of leukocytoclastic vasculitis consist entirely of petechiae; ecchymoses are not found. Moreover, since the petechiae form in association with the presence of a perivascular inflammatory infiltrate, the petechiae are usually at least slightly palpable. This accounts for one of the synonyms for this disease: palpable purpura. Other synonyms include hypersensitivity angiitis, allergic vasculitis, and necrotizing vasculitis.

The smallest lesions of neutrophilic vasculitis occur as pinpoint dots that, early in the course of the disease, are bright red. As the lesions age, they become increasingly violaceous or even blue-black. The smallest lesions may not be palpable, but they are usually accompanied by at least a few larger, palpable papules. These larger lesions are sharply marginated violaceous papules 2 to 10 mm in diameter. They are characterized by the presence of a minute centrally located blue-black infarct or a tiny hemorrhagic vesicle. Both to the small and the large lesions of neutrophilic vasculitis fail to blanch when they are compressed by a glass microscope slide. The lesions are asymptomatic.

The lesions of vasculitic purpura develop on the lower legs first and in more severe cases may then spread to the rest of the body. Some clustering of lesions, particularly over joints, is often notable.

The lesions of vasculitic purpura are easily recognizable clinically. Biopsy should be used to confirm a suspected diagnosis.

Atypical Presentations. Anaphylactoid purpura (Henoch-SchOnlein purpura) is a neutrophilic vasculitic disease occurring primarily in children. The skin lesions are quite similar, though larger (2- to 3-cm) plaques are usually intermingled with the more classical purpuric papules. Additionally, immunoglobulin A (IgA) rather than immunoglobulin G (IgG) is present around the cutaneous blood vessels. Renal and gastrointestinal lesions are regularly present.

Course and Prognosis

The prognosis of vasculitic purpura depends largely on whether or not internal organs are involved. When there is no internal involvement, there is little morbidity, and the disease runs an uneventful course over 2 or 3 weeks. On the other hand, involvement of the nervous system, kidneys, or lungs results in considerable morbidity and even the possibility of death. Intermediate syndromes with only skin, joint, and gastrointestinal involvement are also encountered.

Pathogenesis

Leukocytoclastic vasculitis is characterized by a neutrophilic inflammatory response in and around small blood vessels. This feature identifies the disease as an example of vascular wall purpura (cf. intravascular and extravascular purpura).

Therapy

Milder cases of vasculitic purpura require no therapy at all. Systemically administered steroids are required when there is internal organ involvement. The response to such therapy is good, but relapse often follows cessation of steroid usage. Results of some reports suggest that nonsteroidal anti-inflammatory agents such as colchicine, indomethacin, and dapsone are of help. Antihistamines, while often administered, do not seem to be particularly effective.