Behçet's disease laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hamid Qazi, MD, BSc [2]
Overview
The laboratory tests used to diagnose Behçet's disease are a pathergy test, a skin biopsy, and a lumbar puncture.
Laboratory Findings
Lack of Specific Biomarkers
Behçet’s has no pathognomonic laboratory or histologic diagnostic test.
Laboratory tests are mainly used to exclude other differential diagnoses.
- Genetic Associations
HLA-B*51: strongest genetic risk factor, but its high prevalence in the general population limits diagnostic utility.
Other genes (ERAP1, IL23R–IL12RB2, STAT4, IL10, TNFAIP3, MEFV, TLR4, NOD2, FUT2) linked through GWAS, but not used as routine clinical tests.
- Inflammatory and Immunologic Findings
Innate and adaptive immune abnormalities noted:
↑ Th1 cytokines (TNF-α, IFN-γ).
↑ Th17 cytokines (IL-17, IL-23).
↓ Regulatory T-cell activity.
Neutrophils: hyperactive, producing excess reactive oxygen species (ROS) and releasing neutrophil extracellular traps (NETs).
NF-κB pathway: heightened activity in antigen-presenting cells, neutrophils, and T-helper cells.
- Histopathology
Biopsy specimens (e.g., skin):
Leukocytoclastic vasculitis.
Neutrophilic or lymphocytic perivascular infiltrates.
Microvascular thrombi.
Neutrophilic dermal infiltrates.
- Laboratory Workup in Differential Diagnosis
When evaluating mucocutaneous and systemic manifestations, suggested labs include:
Blood tests: CBC, CRP, iron, zinc, folate, vitamins B1, B6, B12.
Immunologic tests: ANA, anti-desmoglein antibodies, anti-transglutaminase antibodies, HLA-B27, ACE levels.
Infectious serologies: HIV, herpes, syphilis, CMV, tuberculosis testing as indicated.
Coagulation/thrombophilia screening for vascular events (e.g., antiphospholipid antibodies, myeloproliferative syndromes).
- Pathergy test: During this procedure, the skin of the forearm is pricked with a sterile needle. After 24~48 hours, a red nodule or pustule greater than two millimeters in diameter suggests positive and Behçet's syndrome.[1]
- Skin biopsy: Skin biopsy is used to diagnose a skin condition such as a rash and exclude skin cancer. During the procedure, a thin slice off the top of the skin is taken and the lesions are removed.
- Lumbar puncture: When the presentation is a severe headache and head CT is normal, then lumbar puncture can be done to exclude other center nervous diseases of headache. During this procedure, the patient lies on the side, with knees pulled up toward the chest, and chin tucked downward. After injecting the anesthetic into the lower spine, the doctor inserts a spinal needle into the lower back area to measure CSF pressure and collect a sample.[2]
- No specific laboratory test result is diagnostic of Behçet syndrome.
- Serum complement levels are within the reference range, except for just prior to eye or mucous membrane involvement, at which time they may be decreased.
- Sedimentation rate or C-reactive protein may be elevated. Chronic anemia common, and a neutrophil leukocytosis is seen in about 15% of patients.
- Human leukocyte antigen (HLA)-B51 may be present in patients of Asian, Mexican, or Middle Eastern descent.[3]
- Anticardiolipin antibodies are present in as many as 30% of patients.
- Systemic lupus erythematosus and other vasculitic syndromes must be ruled out. Patients with Behçet syndrome have negative antinuclear and antineutrophilic cytoplasmic antibodies.
- In patients with CNS findings, cerebral spinal fluid pleocytosis may be present.
- In addition to thrombosis associated with antiphospholipid antibodies, thrombosis has been reported in Behçet syndrome associated with factor V Leiden mutations and with prothrombin G20210A mutations.[2][4]
References
- ↑ Assar S, Sadeghi B, Davatchi F, Ghodsi SZ, Nadji A, Shahram F; et al. (2017). "The association of pathergy reaction and active clinical presentations of Behçet's disease". Reumatologia. 55 (2): 79–83. doi:10.5114/reum.2017.67602. PMC 5442298. PMID 28539679.
- ↑ 2.0 2.1 Seyahi E, Cakmak OS, Tutar B, Arslan C, Dikici AS, Sut N; et al. (2015). "Clinical and Ultrasonographic Evaluation of Lower-extremity Vein Thrombosis in Behcet Syndrome: An Observational Study". Medicine (Baltimore). 94 (44): e1899. doi:10.1097/MD.0000000000001899. PMC 4915888. PMID 26554787.
- ↑ Akpolat T, Koç Y, Yeniay I, Akpek G, Güllü I, Kansu E; et al. (1992). "Familial Behçet's disease". Eur J Med. 1 (7): 391–5. PMID 1341477.
- ↑ Saadoun D, Wechsler B, Resche-Rigon M, Trad S, Le Thi Huong D, Sbai A; et al. (2009). "Cerebral venous thrombosis in Behçet's disease". Arthritis Rheum. 61 (4): 518–26. doi:10.1002/art.24393. PMID 19333987.