Small vessel vasculitis, cutaneous L95.5

Classification according to vessel size and type of inflammation: This classification subdivides vasculitides according to objectifiable histopathological criteria that take into account, on the one hand, the size of the vessels (small, medium, and large) and the type and composition of the infiltrate (e.g., the significant criterion of leukocytoclasia). "Small vessel" refers to capillaries, arterioles, and venules; "medium-sized vessel" refers to middle arterial and venous vessels; and "large vessel" refers to the aorta and its direct branches or its branches (e.g., temporal artery). Even with this primarily histomorphologic classification, there are uncertainties and overlaps, especially when clinical and histologic entities are used synonymously. For example, multiple clinical entities underlie leukocytoclastic vasculitis (LcV). The common feature of this group is the exclusively histologically detectable pathologic substrate, namely vasculitis with neutrophil leukocyte decay, leukocytoclasia. Thus, even this classification is ultimately unsatisfactory from a clinical point of view.

Histopathological and immunological classification and assignment of clinical entities (based on Sundkötter). 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.

• 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
    Urticariavasculitis:
    • Hypocomplementemic urticarial vasculitis.
    • Normocomplementemic urticarial vasculitis.
    • Serum sickness
    • Vasculitis associated with 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).

In immunocomplex vasculitis, the detection of perivascular immunoglobulins by means of direct immunofluorescence (DIF) serves to confirm the diagnosis on the one hand and to detect the form of vasculitis (IgA, IgG/IgM, rheumatoid or cryoglobulinemic vasculitis) on the other. The earliest possible lesions should be examined bioptically. In serial examinations of vasculitic lesions, at least 1 immunoglobulin was found in >90%, mostly IgA (85%), with or without IgG or IgM, in 7% no IgA, but IgG or IgM. Of the IgA-positive patients, 15% had a systemic form of vasculitis and 83% had a form limited to the skin (Herda L et al. 2025).

S. Vasculitis

Herda L et al. (2025) High percentage of positive direct immunofluorescence in immune complex v asculitis. JDDG 23:479-486