Diagnosis of Behçet's Syndrome
Behçet's syndrome is diagnosed clinically when a patient presents with recurrent oral aphthous ulcers (mandatory criterion) plus at least two of the following: recurrent genital ulceration, uveitis/retinal vasculitis, specific skin lesions (particularly erythema nodosum-like lesions), or positive pathergy test. 1
Essential Diagnostic Criteria
The diagnosis requires:
- Recurrent oral aphthous ulcers (mandatory - must be present) 1
- Plus at least 2 of the following 4 criteria: 1
- Recurrent genital ulceration (look for active ulcers or scarring from chronic ulceration) 1
- Uveitis or retinal vasculitis on complete ophthalmologic examination 1
- Specific skin lesions (erythema nodosum-like lesions carry more diagnostic weight than papulopustular/acne-like lesions) 1
- Positive pathergy test 1
Critical Clinical Examination Steps
Mucocutaneous Assessment
- Perform thorough genital examination to identify genital ulcers or scars, as chronic genital ulceration can cause obliterative and deforming scarring that requires aggressive treatment 1
- Distinguish skin lesion types: erythema nodosum-like lesions are more diagnostically significant than acneiform lesions 1
- Evaluate for papulopustular lesions, though these have less diagnostic weight 1
Mandatory Ophthalmologic Evaluation
- Complete ophthalmologic examination is mandatory to assess for uveitis or retinal vasculitis, as ocular involvement is both a diagnostic criterion and a poor prognostic factor 1
- Regular ophthalmologic examinations are essential throughout disease course 1
Supportive Laboratory Testing
HLA-B51 Testing
- HLA-B51 has moderate positive predictive value (~55%) and high negative predictive value (84-90%) 1
- Should NOT be used as standalone diagnostic test - only as supportive evidence 1
- HLA-B51 is the strongest genetic susceptibility factor 2, 3
Inflammatory Markers
- ESR or CRP can monitor inflammatory activity but are not specific to Behçet's disease 1
- Complete blood count to check for anemia, leukocytosis, or thrombocytosis 1
Organ-Specific Evaluations for Poor Prognostic Features
High-Risk Organ Involvement Assessment
The presence of ocular, vascular, neurological, or gastrointestinal involvement indicates poor prognosis and requires aggressive treatment 1:
- Vascular involvement (occurs in ~1/3 of patients): Doppler ultrasound, CT angiography, or MR angiography to evaluate arterial and venous manifestations 1
- Neurological involvement: MRI with contrast is imaging modality of choice; CSF analysis may show pleocytosis and elevated protein 1
- Gastrointestinal involvement: Confirm through endoscopy and/or imaging; rule out NSAID-induced ulcers, inflammatory bowel disease, and tuberculosis 1
Critical Differential Diagnoses to Exclude
When neurological involvement is present, exclude: 1
- Multiple sclerosis
- Neurosarcoidosis
- CNS vasculitis
For gastrointestinal symptoms, exclude: 1
- Crohn's disease
- NSAID-induced ulcers
- Tuberculosis
Risk Stratification
Young men with early disease onset have the most severe disease course and require more aggressive treatment and closer follow-up 4, 5
Common Pitfalls to Avoid
- Do not rely on HLA-B51 testing alone for diagnosis - it is only supportive 1
- Do not overlook genital examination - scarring from healed ulcers may be the only finding 1
- Do not skip ophthalmologic examination - eye involvement can be asymptomatic initially but leads to blindness if untreated 1
- Do not assume all skin lesions are equal - erythema nodosum-like lesions are diagnostically more significant than acneiform lesions 1