Vasculitis (overview)L95.8

Inflammation of blood vessels caused by a characteristic, phased inflammatory process in the walls of various types of blood vessels, which leads to various clinically and/or histopathologically defined clinical and/or histopathological clinical pictures (clinical-pathological entities).

The classification of vasculitis is unsatisfactory, as the aetiology and pathogenesis of this heterogeneous group of diseases is still poorly understood. In the following, various common classification systems are juxtaposed without prejudice.

In clinical dermatology in particular, historically based, predominantly descriptive diagnostic entities continue to be used, which are not readily reflected in the current classifications, but are of relevant use in everyday clinical practice. The classification that most closely reflects the dermatological entities is that of Sunderkötter et al:

• Classification according to "primary" and "secondary" vasculitis. This classification is not always reproducible, especially as there are wide areas of overlap between the two:
  • Primary vasculitis: The triggering cause remains unknown. The pathogenesis is based on an immunological "hypersensitivity reaction". Autoantibodies against neutrophil granulocytes and/or endothelial cells (ANCA/AECA) as well as immunohistologic examinations are necessary for clarification.
  • Secondary vasculitis: vasculitis in the context of underlying diseases (e.g. infections, collagenoses, in rheumatoid arthritis(rheumatoid vasculitis), can also be triggered by numerous medications).
• Classification according to immunological causes. A distinction is made between:
  • ANCA-associated vasculitis(granulomatosis with polyangiitis (GPA); microscopic polyangiitis (MPA); eosinophilic granulomatosis with polyangiitis (E-GPA); special form: drug-induced ANCA-positive vasculitis)
  • Immune complex vasculitis (leukocytoclastic vasculitis)
  • Pauci-immune vasculitis
  • T-cell-mediated granulomatous vasculitis.
• Classification according to vessel size and type of inflammation:
  • This classification divides the vasculitides according to objectifiable histopathological criteria, which take into account the size of the vessels (small, medium and large) and the type and composition of the infiltrate (e.g. the important criterion of leukocytoclasia). " Small vessels" are capillaries, arterioles and venules; "medium-sized vessels" refers to medium-sized arterial and venous vessels and"large vessels" to the aorta and its direct branches or their branches (e.g. temporal artery). Even with this morphological classification, there are imprecisions and overlaps, especially when clinical and histological entities are used synonymously. For example, leukocytoclastic vasculitis (LcV) is based on several clinical entities. The common feature of this group is the exclusively histologically detectable pathological substrate, namely vasculitis with the decay of neutrophilic leukocytes, leukocytoclasia. This classification is therefore ultimately unsatisfactory from a clinical point of view.
• Histopathological and immunological classification and assignment of clinical entities (based on Sunderkötter). It has been shown that the occurrence of IgA-containing immune complexes (detection by DIF) has a significant prognostic (rather unfavorable prognosis) and therapeutic significance.
• Vasculitis of small vessels (cutaneous small vessel vasculitis [CSVV]):
  • LcV, largely IgA-associated:
    • Schönlein-Henoch purpura
    • Infantile, acute, hemorrhagic edema (age < 2 years)
  • LcV (non-IgA-associated)
    • LcV (non-IgA-associated) - with/without systemic involvement.
    • Urticarial vasculitis:
      • Normocomplementemic urticarial vasculitis
      • Hypocomplementemic urticarial vasculitis.
    • Serum sickness
    • Vasculitis in essential cryoglobulinemia
  • Other (special forms):
    • Granuloma (eosinophilicum) faciei
    • Erythema elevatum diutinum
    • Septic vasculitis
    • Purpura fulminans
    • LcV with eosinophilia (entity questionable)
    • LcV in collagenoses (SLE, scleroderma).
• Vasculitis of medium-sized vessels:
  • Systemic (ANCA-positive) vasculitis:
    • Granulomatosis with polyangiitis (Wegener's granulomatosis)
    • Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome)
  • Polyarteritis nodosa (PAN) group:
    • Polyarteritis nodosa, systemic
    • Microscopic polyangiitis (polyarteritis nodosa microscopic)
    • Polyarteritis nodosa, cutaneous
  • Other:
    • Nodular vasculitis (erythema induratum)
    • Kawasaki syndrome.
• Vasculitis of large vessels:
  • Temporal arteritis
  • Takayasu arteritis

The histological classification of a vasculitic process is performed in 3 steps (Ratzinger et al. 2015):

• 1. overview magnification: differentiation between small and medium-sized vessels
• 2. medium magnification: definition of the vessels affected - capillaries vs. post-capillary venules, arteries vs. veins - .
• 3. high magnification: definition of the cell infiltrate (leukocytoclastic, granulomatous, other infiltrate). Note: Vasculitis is always accompanied by an infiltrate in the vascular wall.

Trigger of secondary vasculitides

Clinical classification of primary vasculitides (Chapel Hill Consensus Conference)

Therapeutic strategies for vasculitis (after Fiorentino)

Algorithm for diagnostic clarification in vasculitis (modified according to Fiorentino)

Phlebitides as vascular wall inflammations of larger trunk and extremity veins are also "vasculitides". However, they do not belong to the vasculitides listed here in the narrower sense. This also applies to endangiitis obliterans, which, as an independent vasculitic clinical picture with obligatory occlusive symptoms, is rather classified as an arterial occlusive disease. In many classifications, the term " vasculopathy" is also used, a general term for primarily non-inflammatory vascular diseases associated with partial or complete occlusion of a vessel (e.g., livedo racemosa). Because vasculitides of the skin organ are often associated with focal hemorrhage, the descriptive term "purpura" (e.g., Schönlein-Henoch purpura, anaphylactoid purpura, et al.) has been used in previous literature as a clinical diagnosis for an underlying "hemorrhagic leukocytoclastic vasculitis." The term"purpura" contains a vagueness dictated by history that we will not correct here.

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