DIAGNOSIS

 

DIAGNOSIS AND DISEASE MONITORING

Disease definition

There is no specific test for Behçets disease, and the diagnosis is based upon clinical criteria.A number of classifications have been formulated, each with its own list of clinical features. In1990, these were amalgamated into the International Study Group Classification criteria (Table 1). These have now been widely adopted, and although intended for the definition of patients participating in research programmes rather than for the diagnosis of individual patients, they also perform well in a clinical context.

Differential diagnosis

Although the diagnosis of Behçets disease may be straightforward once the possibility has been recognized, incomplete disease or unusual presentations often represent a diagnostic challenge.

 

Table 1.

International study group criteria for the diagnosis of Behçets disease.

 
Recurrent oral ulceration Minor aphthous, major aphthous or herpetiform ulceration observed by physician or patient, which have recurred at least three times in a 12-month period
   
  And two of the following
   
Recurrent genital ulceration Aphthous ulceration or scarring, observed by physician or patient
   
Eye lesions Anterior uveitis, posterior uveitis, or cells in vitreous on slit lamp
examination; or retinal vasculitis observed by ophthalmologist
   
Skin lesions Erythema nodosum observed by physician or patient, pseudofolliculitis or papulopustular lesions; or acneiform nodules observed by the physician in post-adolescent patients not on corticosteroid treatment
   
Positive pathergy test Read by physician at 24–48 hours
   

The findings are applicable only in the absence of other clinical explanations.

 A detailed clinical history is essential to exclude other conditions and reveal subtle features of this complex disease. Reiter’s syndrome may be associated with oral and genital ulcers, although the arthritis is generally erosive. Urethritis and sacroileitis are not features of Behçets disease.

Sarcoidosis can also present with erythema nodosum, uveitis and arthralgia, but genital ulcers are not a feature. Chest radiography may be helpful. Stevens-Johnson syndrome also presents with mucocutaneous involvement and conjunctivitis but is not associated with thrombophlebitis, uveitis or arterial disease. There is a considerable clinical overlap between Crohn’s disease and ulcerative colitis with extragastrointestinal involvement, and Behc¸et’s disease with predominantly gastrointestinal involvement. Other causes of periodic fevers, such as familial Mediterranean fever, hyper IgD syndrome or periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis (PFAPA) syndrome, should be considered in children as recurrent febrile episodes may characterize the onset of Behc¸et’s disease. Patients with significant neurological involvement may occasionally be misdiagnosed as having multiple sclerosis. Other chronic systemic diseases associated with recurrent aphthous ulceration include systemic lupus erythematosus and celiac disease. Recurrent orogenital ulceration may also be associated with bullous skin disorders and erythema multiforme.

Laboratory investigations

Laboratory findings are non-specific in Behçet's disease. Moderate anaemia of chronic disease is common, and a neutrophil leukocytosis is seen in 15% of patients. Serum immunoglobulins may be non-specifically elevated. Autoantibodies such as rheumatoid factor, anti-nuclear antibody and anti-neutrophil cytoplasmic antibody are usually negative. Importantly, non-specific markers of inflammation such as C-reactive protein level and erythrocyte sedimentation rate can be normal despite active orogenital, ocular or CNS disease.62 HLA typing is generally not useful in a diagnostic context because of the lack of sensitivity of the association with HLA-B*51.
Disease activity index In the absence of any specific marker of disease activity, monitoring of the disease is primarily clinical. This has been recently facilitated by the publication of a disease activity index: the Behc¸et’s Disease Current Activity Form is a convenient and logical tool, and can easily be administered during the course of a routine consultation to provide a standard for comparison.

 

My Gratitude to Sara E. Marshall* MB BCh, MRcp (Ire), MRcPath (UK), PhD

Senior Lecturer in Immunology Wright Fleming Institute, Imperial College School of Medicine, London for providing this information