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Antinuclear antibodies (ANA) are a common diagnostic finding in patients with systemic autoimmune diseases. In patients with typical clinical symptoms, the determination of ANA is of both diagnostic and prognostic importance. However, if ANA were determined due to unspecific symptoms, the interpretation of ANA findings can be problematic. In these cases, misjudgements with severe consequences for the patients are possible. Many systemic autoimmune diseases have prominent early skin involvement and the dermatologist can be the first physician that such a patient sees. Therefore, knowledge of ANA diagnostics is important for dermatologists. Basic principles of autoantibody diagnostics, guidance for the interpretation of laboratory results and new developments are discussed in this overview.

Raynaud's phenomenon (RP) is a painful vasospasm of small arteries, localised in fingers and toes. Typically these body parts turn white (ischemia), then blue (deoxygenation) and then red (reperfusion). Two different types of RP exist: the common primary RP without underlying disease and the rare secondary RP, mostly associated with rheumatoid diseases such as systemic sclerosis. Thus, the dermatologist has to be aware of this condition. In this article the clinical criteria, differential diagnoses, diagnostic considerations and treatment options are discussed.

The skin is one of the organs most frequently involved in vasculitides. Cutaneous vasculitis may present (1) part of a systemic vasculitis (e.g., IgA vasculitis), (2) a skin-restricted or skin-dominant variant of the corresponding systemic vasculitis without clinically apparent visceral involvement (e.g., cutaneous IgA vasculitis), or (3) a vasculitis occurring exclusively in the skin (e.g., erythema elevatun diutinum). The clinical symptoms of vasculitides are markedly determined by the size of the predominantly affected blood vessels. Systemic polyarteritis nodosa is regarded as a medium vessel vasculitis and is associated with multiple skin symptoms: (1) vasculitis of digital arteries with ensuing digital infarction, (2) livedo racemosa and subcutaneous nodules, and (3) in some patients even purpura and hemorrhagic macules due to additional small vessel vasculitis. In contrast, in its skin-restricted entity (i.e., cutaneous polyarteritis nodosa), the predominant symptoms are subcutaneous nodules surrounded by livedo racemosa, often on the lower legs. Among small-vessel vasculitides palpable purpura with predilection for the legs is a nearly pathognomonic feature of immune complex vasculitis. Variations in clinical symptoms indicate additional pathophysiological mechanisms or different vascultides: (1) ANCA-associated vasculitides often also entail nodules or sometimes livedo, (2) cryoglobulinemic vasculitis additionally may present with necrosis at cold exposed areas and involvement of vessels of various size, (3) small vessel vasculitis associated with systemic lupus erythematosus or rheumatoid arthritis shows predilection for additional sites (e.g., nailfolds) and also involvement of vessels beyond postcapillary venules, (4) recurrent macular vasculitis in hypergammaglobulinemia also occurs on dependent parts, but shows numerous small hemorrhagic macules instead of palpable purpura, (5) erythema elevatum diutinum begins with brightly red to violaceous plaques at extensor sites, followed by fibrotic nodules. Consequently, cutaneous symptoms provide pivotal clues for further diagnosis and ensuing management of vasculitides.