Dermatologic Aspects of Behcet Disease Workup

Updated: May 13, 2019
  • Author: Amira M Elbendary, MBBCh, MSc; Chief Editor: William D James, MD  more...
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Workup

Laboratory Studies

Mild anemia and leukocytosis are observed in some patients with chronic disease.

The erythrocyte sedimentation rate, C-reactive protein value, and other acute phase reactants may be elevated during the active stage of Behçet disease, but they do not correlate well with the clinical activity.

An increase in alpha-2 globulins is often observed. Serum immunoglobulin levels, especially immunoglobulin A, may be elevated.

Circulating immune complexes are often present.

Rheumatoid factor and antinuclear antibodies are absent.

Antineutrophil cytoplasmic antibody and antiphospholipid antibody test results are usually negative.

Human leukocyte antigen (HLA) typing can be performed as patients with the HLA-B51 allele have a significantly higher risk of developing Behçet disease.

Lumbar puncture for cerebrospinal fluid analysis can be performed when neuro-Behçet syndrome is suspected. In cases of parenchymal neuro-Behçet syndrome, the spinal fluid demonstrates elevated protein levels and a neutrophilic pleocytosis, which may later show transition to a lymphocytic predominance.

Positive pathergy test

The testing methodology varies in different institutions. However, the most common method is using a 20- to 26-g needle and performing 4-6 intradermal punctures in the flexor region of the forearm at an angle of 45º and reading the site at 48 hours. [122] The reaction is considered positive if an erythematous papule forms, sometimes topped with a sterile pustule greater than 2 mm in diameter. In smaller lesions and suspicious cases, histopathologic examination can help. An inflammatory infiltrate with predominant perivascular mononuclear cells and mast cells are typical findings. Neutrophilic vasculitis may be present. [122]

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Imaging Studies

Echocardiography is important to exclude the presence of cardiac thrombi, which carry high morbidity and mortality if not diagnosed early. Right atrial and ventricular thrombi respond well to aggressive anti-inflammatory therapy.

In a study of 63 Behçet disease patients with cardiac involvement, the most common findings noted were prolapsed valves with aneurismal changes, echo-free spaces within the annulus, and vegetationlike lesions. The second most common form of involvement was aortic lesions in the form of aortic aneurysm or dilatation, or aortic pseudoaneurysm. Other findings included pulmonary aneurysm, coronary arterial pseudoaneurysm, and pericardial effusion. [123]

Magnetic resonance imaging (MRI) is the criterion standard for the diagnosis of neuro-Behçet disease. The MRI findings are dependent on the part affected: whether it is parenchymal or nonparenchymal.

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Histologic Findings

The etiology and pathogenesis of Behçet disease remain obscure, although many reviews describe a lymphocytic vasculitis.

Vasculitis is thought to affect vessels of all sizes; the various skin lesions are thought to be secondary to small vessel vasculitis.

The histopathology is variable, dependent upon the type of lesion. Pathergic lesions are characterized by a heavy neutrophilic infiltrate without fibrin within the vessel walls. Folliculitis, acneiform lesions, and dermal abscesses have been described in Behçet disease.

The erythema nodosum–like lesions show a perivascular lymphocytic infiltrate of lymphocytes in the deep dermis and septa with a lymphocytic vasculitis but lack the histiocytic granulomas of typical erythema nodosum.

The aphthous ulcers have a nonspecific pathology with a variable infiltrate of lymphocytes, macrophages, and neutrophils at the base of the ulcer.

T-cell subsets with a preponderance of helper-inducer cells over T suppressor-cytotoxic cells have been observed in lesions.

Electron microscopic observations

Examination of erythema nodosum–like lesions shows microvascular changes and lymphocyte-mediated fat cell lysis. Additionally, small dermal blood vessels embolized by thrombi are observed at the sites of the needle prick reaction (pathergy) and at the erythema nodosum–like lesions.

The early changes in fat cells may be caused by vascular changes brought about by the specific degeneration of endothelial cells and vascular stenosis associated with the delayed-type hypersensitivity reaction.

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Other Tests

Capsule endoscopy was evaluated in a case control study that included 19 patients with intestinal Behçet disease   and may have diagnostic value in patients with intestinal involvement. [124]

Bone scintigraphy for Behçet disease patients presenting with nonspecific arthralgia without significant signs was found to be of value in assessing joint involvement and specifying the sites of involvement. [125]

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