musculoskeletal and connective tissue disorders
Cutaneous Vasculitis
Diagnosis of Cutaneous Vasculitis
Exclusion of clinically evident causes of systemic vasculitis Routine tests (eg, complete blood count, erythrocyte sedimentation rate, urinalysis, serum creatinine, chest x-ray) Biopsy Tests to identify the type and etiology of vasculitis (eg, cryoglobulins, antineutrophil cytoplasmic antibodies, hepatitis B and C antibodies, C3 and C4 complement levels, rheumatoid factor, blood cultures, protein electrophoresis) A diagnosis of vasculitis limited to the skin requires a complete history and physical examination. Evaluation is focused at identifying causes, such as new drugs or infections, and excluding manifestations of inflammation or vasculitis in other organs, such as Lungs: Shortness of breath, cough, hemoptysis, and signs of consolidation Kidneys: New-onset hypertension or edema Nerves: New-onset asymmetric weakness or paresthesias Intestine: New-onset abdominal pain, diarrhea, and bloody stools Urinalysis should exclude blood, protein, and red blood cell casts. A chest x-ray is needed to check for infiltrates (suggesting alveolar hemorrhage). Complete blood count and other blood tests are needed to check for anemia, to determine platelet count and serum creatinine level, and to check for elevated levels of acute-phase reactants (eg, erythrocyte sedimentation rate, C-reactive protein). Leukopenia and thrombocytopenia are not typical of cutaneous vasculitis and prompt consideration of an alternate diagnosis. Skin biopsy should be done, optimally within 24 to 48 hours after vasculitic lesions appear. Diagnostic yield depends on the depth and timing of the biopsy. Generally, deep punch biopsy or excision biopsy into the subcutis is preferred; these biopsies can sample small- and medium-sized vessels. Shave biopsy is usually inadequate. If histologic examination detects the following, cutaneous vasculitis is confirmed: Infiltration of the vessel wall by inflammatory cells, resulting in disruption and destruction of the vessel wall Intramural and intraluminal fibrin deposition (fibrinoid necrosis) Extravasation of red blood cells Nuclear debris (leukocytoclasis) Direct immunofluorescence staining is needed to check for IgA, IgM, and IgG and complement deposition in and around the vessel wall, which suggests an immune complex–mediated process, a myeloid or lymphoproliferative disorder, or other neoplastic disorder, especially in adults. IgA deposition has been associated with renal, joint, and gastrointestinal manifestations, but IgG and IgM have not. Direct immunofluorescence staining may be positive for IgM or IgG in cryoglobulinemic vasculitis or rheumatoid arthritis and for IgA in immunoglobulin A–associated vasculitis. Tests done to identify the cause of vasculitis include cryoglobulins, antineutrophil cytoplasmic antibodies (ANCA), hepatitis B and C antibodies, C3 and C4 levels, rheumatoid factor, blood cultures, and serum and urine protein electrophoresis. Other tests are done as needed to identify clinically suspected causes of vasculitis. 