musculoskeletal and connective tissue disorders
Overview of Vasculitis
Diagnosis of Vasculitis
Clinical evaluation Basic laboratory tests to detect inflammation or organ dysfunction (eg, complete blood count [CBC], erythrocyte sedimentation rate [ESR] or C-reactive protein, serumalbuminand total protein, aspartate aminotransferase [AST] and alanine aminotransferase [ALT], bloodureanitrogen [BUN] and creatinine, urinalysis) and to stage disease process Laboratory tests to help determine the type of vasculitis (eg, antineutrophil cytoplasmic antibodies [ANCA]) if suggested by clinical assessment Laboratory and imaging studies that may help determine the cause of vasculitis (eg, cryoglobulins, hepatitis B surface antigen test, hepatitis B core and hepatitis B surface antibody tests and hepatitis C virus antibody test, , blood cultures) and extent of organ involvement Biopsy Systemic vasculitis is suspected in patients with the following: Symptoms or signs suggestive of vasculitis (eg, temporal headache and jaw claudication suggesting giant cell arteritis) Ischemic manifestations (eg, ischemic stroke, limb claudication, mesenteric ischemia) out of proportion to a patient's risk factors for atherosclerosis Unexplained combinations of symptoms in more than one organ system that are compatible with vasculitis (eg, hypertension, myalgias, hemoptysis), particularly when symptoms of a systemic illness are present Primary vasculitic disorders are diagnosed based on the presence of characteristic symptoms, physical findings, compatible laboratory test results, and exclusion of other causes (ie, secondary vasculitis). Histologic examination is done whenever possible and may support the diagnosis of a particular vasculitic disorder (see table). Clinical findings determine the differential diagnosis and thus direct laboratory testing. Most routine laboratory tests yield results that are nonspecific and must be interpreted in the context of the entire clinical presentation. However, results can often help support the diagnosis, determine the location and degree of organ involvement, or suggest alternative diagnoses. Tests usually include CBC, ESR or C-reactive protein, serumalbuminand total protein, AST, and ALT. Often, patients present with elevated ESR or C-reactive protein, anemia due to chronic inflammation, elevated platelets, and low serumalbumin. Freshly voided urine must be tested for red blood cells, red blood cell casts, and protein to identify renal involvement. Serum creatinine levels should be checked and monitored. Leukopenia and thrombocytopenia are not typical of primary vasculitis and suggest an alternate diagnosis. Detection of antineutrophil cytoplasmic antibodies (ANCA) may support the diagnosis of Granulomatosis with Polyangiitis (GPA) (GPA), Other useful laboratory tests include hepatitis B and C serologic testing, serum and urine protein electrophoresis, antinuclear antibody and anti-extractable nuclear antigens panel, testing for the presence of cryoglobulins, and complement levels. Complement levels may be low in viral vasculitis, cryoglobulinemic vasculitis, lymphoproliferative disorders, or vasculitis secondary to other autoimmune diseases. Further testing is determined by clinical findings. If indicated based on clinical findings, a chest x-ray should be done to check for infiltrates, but high-resolution noncontrast CT of the chest may be needed to check for subtle findings, such as small nodules or cavities. Bilateral diffuse infiltrates suggest possible alveolar hemorrhage, which requires immediate diagnosis and treatment. Other imaging tests may be required. For example, magnetic resonance angiography of large blood vessels and the aorta is useful for diagnosis and monitoring when such vessels appear affected. If symptoms and examination suggest a neuropathy, electromyography may be helpful. Because vasculitic disorders are rare and treatment may have severe adverse effects, tissue biopsy is done to confirm the diagnosis whenever possible. Clinical findings suggest the best site for biopsy. Biopsy results are most likely to be positive if taken from affected lung, skin, and kidney tissue. Blind biopsies of organs without clinical manifestations or laboratory suggestion of involvement have a low likelihood of providing positive results. 