Pediatric Takayasu Arteritis Workup

Takayasu arteritis (Takayasu arteritis) has no specific markers. However, the following results can be found in laboratory studies:

• Complete blood count (CBC) reveals a normochromic, normocytic anemia in 50% of patients with Takayasu arteritis; acute phase reactants are elevated, with leukocytosis and thrombocytosis
• Westergren erythrocyte sedimentation rate is elevated
• Comprehensive metabolic profile may indicate elevated transaminases and hypoalbuminemia
• The von Willebrand factor–related antigen (factor VIII–related antigen) may be elevated
• Antiendothelial antibodies are present
• Antinuclear antibody results are usually negative
• Rheumatoid factor is elevated in 15% of individuals with Takayasu arteritis
• Increased levels of immunoglobulins G, M, and A are present

Patients with ischemia in all 4 extremities may have falsely low peripheral blood pressures. Accurate blood pressure monitoring in such patients can be obtained reliably only by central systemic measurements.

Arteriography is the criterion standard for assistance in the diagnosis of Takayasu arteritis. It is performed either with invasive angiography or with MRA. (The use of MRA is rapidly increasing.)

Peripheral blood pressure monitoring is frequently inaccurate in persons with Takayasu arteritis; pressure readings during angiography alone may reveal aortic root hypertension.

Arteriography often demonstrates long, smooth, tapered narrowings or occlusions. Some authors recommend arteriography of the entire aorta.

Stenoses occur in 90-100% of patients with Takayasu arteritis, and aneurysm formation in only 27%. Three-dimensional MRA imaging of the aorta and its branches are providing exciting new data that may improve the understanding of the disease. Drawbacks to arteriography, including morbidity from the use of contrast dye in patients with renal disease and cumulative radiation exposure over time, can be avoided by using MRA.

CT scanning and magnetic resonance imaging (MRI) are useful for serial examinations and diagnosis in the early phase of Takayasu arteritis. They may reveal mural thickening of the aorta and luminal narrowing.^{[9, 10]} (See the images below.)

Use of contrast may reveal inflammatory lesions prior to the development of stenoses; these lesions may be missed by angiography. Aortic lesions, including stenosis, dilatation, wall thickening, and mural thrombi, are well visualized on MRI, which is less adequate in visualizing distal lesions of the subclavian vessels and common carotids. (See the images below.)

Gadolinium-enhanced cardiovascular MRI has also been used to demonstrate myocardial perfusion defects, which may be important in long-term prognosis.

Noncontrast, T2-weighted, short inversion imaging recovery (STIR) images may be used to monitor edema in the aortic wall, which may be a surrogate for inflammation; edema was found in 94% of patients with clinically active disease.

Large vessel edema was found in 56% of patients in clinical remission, similar to the 42-44% of patients in clinical remission who were found to have active vasculitis on pathology from bypass specimens. The prognostic significance of vessel edema is uncertain, as progression of lesions occurs in areas without edema, and progression may be absent from areas with edema on subsequent studies.

Additional imaging studies include the following^{[11, 12]} :

• Gallium-67 radionuclide scan - This scan may demonstrate increased uptake in the aorta and branches
• High-resolution ultrasonography - Duplex Doppler may be used to evaluate and monitor disease in the common carotids and subclavian arteries, with carotid evaluation revealing a homogenous, circumferential thickening of the vessel wall that is distinguishable from atherosclerotic thickening; this imaging study is not useful in evaluating the aorta
• Chest radiography - Chest radiography may reveal widening of the ascending aorta, an irregular descending aorta, aortic calcifications, and rib notching (late findings)
• Echocardiography - Perform echocardiography at baseline to evaluate the aortic valve; Perform follow-up echocardiography as indicated to monitor aortic insufficiency

Mononuclear infiltration of the adventitia with perivascular cuffing of the vasa vasorum occurs early in the disease.

Granulomatous changes may be observed in the tunica media with Langerhans cells and central necrosis of elastic fibers and smooth muscle cells. Later, fibrosis of the media and acellular thickening of the intima may compromise the vessel lumen. Grossly, wrinkling of the intima is found.

Histologic specimens seldom are available, due to the large vessels affected, with the exception of specimens obtained during autopsy and bypass surgery.