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Journal article from the Cleveland Clinic Journal of Medicine

Clinical Features and Diagnosis of
Small-vessel Vasculitis

Carol Langford, MD, MHS

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Abstract

Vasculitis is inflammation of the blood vessel. Granulomatosis with polyangiitis (GPA), microscopic polyangiitis, and eosinophilic GPA  are three small-vessel vasculitic diseases that share certain features, but also have important differences. Distinguishing these entities may influence the diagnostic approach, treatment decisions, and outcomes. Circulating antineutrophil cytoplasmic antibodies (ANCA) characterize all three diseases, although their immunofluorescence patterns and target antigen specificities differ. While the presence of ANCA can suggest these diagnoses, the diseases are best viewed as separate entities, each defined by specific clinical and histologic characteristics.

Vasculitis refers to inflammation of the blood vessel. This inflammation can cause vessel wall thickening that compromises or occludes the vessel lumen, ultimately resulting in organ ischemia. It also can cause vessel wall attenuation that predisposes to aneurysm formation or breach of the vessel integrity with resultant hemorrhage into the tissue.
Vasculitis can be thought of as a primary or secondary process. Primary vasculitides are unique disease entities without a currently identified underlying cause in which vasculitis forms the pathologic basis of tissue injury. Vasculitis can occur secondary to medication exposure or an underlying illness, including infections, malignancy, cryoglobulinemia, and rheumatic diseases (such as systemic lupus erythematosus, rheumatoid arthritis, Sjögren syndrome, or myositis).

Primary vasculitides may differ in epidemiology, such as the age at which they occur and the gender most likely to be affected, their clinical manifestations (including signs, symptoms, and patterns of organ involvement), the diagnostic approach (biopsy, arteriography, and laboratory investigation), treatment (supportive care, glucocorticoids alone, or in combination with other immunosuppressants), and the size of the vessels predominantly affected (large, medium, or small).

Small-vessel vasculitis affects the arteriole, capillary, and venule. An excellent example of small-vessel vasculitis and the one most commonly encountered in clinical practice is cutaneous vasculitis, in which extravasation of erythrocytes from disrupted small vessels is observed histologically, with the clinical sequelae of palpable purpura. Although categorization based on the predominant vessel size that is affected is a helpful way to view these diseases, this is not absolute and each disease has the potential to affect a diverse range of vessels.

This article explores the clinical features and diagnosis of three forms of vasculitis that predominantly affect the small vessels: granulomatosis with polyangiitis (GPA [Wegener’s granulomatosis]), microscopic polyangiitis (MPA), and eosinophilic GPA (Churg-Strauss syndrome).

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