White : Diseases of the Skin - Purpura, Vasculitis, Neutrophilic Dermatoses and Related Disorders

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Gary M. White & Neil H. Cox

Diseases of the Skin

14	Purpura,Vasculities,NeutrophilicDermatoses,and Related Disorders

VASCULITIS

Classification

The classification of vasculitis is complex, for several reasons.

•	The classification may be based on clinical patterns, on histologic features (such as the predominant size of vessels involved or the type of inflammatory infiltrate), on immunologic tests (for example, ANCA-positive vasculitides may be considered together), etc.
•	There is overlap between many of the above (e.g. small-vessel neutrophilic cutaneous vasculitis is a feature of some large-vessel granulomatous vasculitides).
•	Classifications based on systemic features of vasculitis correlate poorly with the type and extent of skin lesions.
•	Some terminology is either of uncertain relevance or applied differently to the original descriptions (e.g. ‘hypersensitivity vasculitis').
•	Some disorders that may not be truly vasculitic overlap into the spectrum of vasculitis (such as the neutrophilic dermatoses).
•	Some syndromes of vascular occlusion (such as cryoglobulinemia) are not initially inflammatory but cause secondary vasculitic inflammation.
•	Some vasculitides overlap into other disease areas; for example, pityriasis lichenoides acuta, which has a lymphocytic vasculitis component, is in some cases associated with lymphoma (Ch.33).

This chapter deals primarily with disorders that are generally accepted as ‘mainstream' vasculitides, using headings that are designed to be clinically useful; it combines the predominant size of vessels involved with the clinical morphology of the skin lesions. A tentative classification is provided in Table 14.2.

Table 14.2 CLASSIFICATION OF VASCULITIS

Small-vessel vasculitis	Larger-vessel vasculitis
Cutaneous small-vessel vasculitis, not further classified Henoch–Schönlein purpura Essential mixed cryoglobulinemia Waldenström hypergammaglobulinemic purpura Associated with collagen vascular disease Urticarial vasculitis Erythema elevatum diutinum Eosinophilic vasculitis Rheumatoid nodules Reactive leprosy Septic vasculitis	Polyarteritis nodosa: microscopic polyarteritis, cutaneous form, systemic form Granulomatous vasculitis: Wegener granulomatosis,allergic granulomatosis of Churg and Strauss, lymphomatoid granulomatosis Giant cell arteritis: temporal arteritis, Takayasu arteritis Larger-vessel vasculitis with collagen vascular disease Nodular vasculitis

Small-vessel vasculitis

Larger-vessel vasculitis

Cutaneous small-vessel vasculitis, not further classified

Henoch–Schönlein purpura

Essential mixed cryoglobulinemia

Waldenström hypergammaglobulinemic purpura

Associated with collagen vascular disease

Urticarial vasculitis

Erythema elevatum diutinum

Eosinophilic vasculitis

Rheumatoid nodules

Reactive leprosy

Septic vasculitis

Polyarteritis nodosa: microscopic polyarteritis, cutaneous form, systemic form

Granulomatous vasculitis: Wegener granulomatosis,allergic

granulomatosis of Churg and Strauss, lymphomatoid granulomatosis

Giant cell arteritis: temporal arteritis, Takayasu arteritis

Larger-vessel vasculitis with collagen vascular disease

Nodular vasculitis

(From Barham KL, Jorizzo JL, Grattan B, et al. Vasculitis and neutrophilic vascular reactions. In: Burns DA, Breathnach SM, Cox NH , et al (eds) Rook's Textbook of Dermatology, 7th edn. Oxford : Blackwell Publishing, 2004.)

Antibodies

A number of tests involving antibodies are of importance in the investigation of vasculitis. Antinuclear antibody and other antibodies discussed in Chapter 13 are often tested, as many of the collagen vascular diseases have a vasculitic component. Direct immunofluorescence (discussed in Ch.16 in the context of bullous dermatoses) is important to detect immune complex vasculitis, in which there are deposits of antibody in cutaneous blood vessels. The type of antibody may also be critical, for example IgA in Henoch–Schönlein purpura (HSP), discussed later.

Antiphospholipid and anticardiolipin antibodies are specifically discussed later in a section on the antiphospholipid syndrome.

Antineutrophil cytoplasmic antibodies (ANCAs) have become an important investigation in diagnosis of large-vessel vasculitides and are discussed in the relevant section of this chapter.