Behcet's disease overview

# Overview
Behcet's disease is a chronic inflammatory condition caused by disturbances in the immune system. The immune system normally protects the body against infections through a controlled inflammatory reaction against the pathogen. In Behcet's disease, the immune response becomes overactive and produces unpredictable outbreaks of exaggerated inflammation. This extra inflammation affects blood vessels, in particular, the smaller vessels. As a result, symptoms appear wherever the exaggerated inflammation response is produced. The inflammatory response can occur anywhere on the body where there is a blood supply.

# Historical Perspective
Behcet disease was first discovered by Hippocrates in the 5th century. In 1937, Hulusi Behcet, Turkish dermatologist described Behcet's disease that genital ulcerations, uveitis, and aphthous ulcers are it's major presentations.

# Classification
Neurologic disease of Behcet disease is classified into parenchymal or non-parenchymal. Parenchymal disease is due to lesions in the corticospinal tract, brainstem, periventricular white matter, spinal cord, and basal ganglia. Focal parenchymal lesions and complications of vascular thrombosis are the most common abnormalities. Progressive personality change, psychiatric disorders, and dementia may develop. Parenchymal disease may be divided into acuteand chronic progressive neuro-Behcet syndrome. Central nervous system lesions are detectable with MRI. In the chronic phase, lesions may be smaller or resolve, atrophy may be present, nonspecific white matter lesions may be present, and lesions usually do not enhance. Cerebrospinal fluid (CSF) may show increased protein and increased cells, and neutrophils may predominate. Non-parenchymal disease of Behcet disease include cerebral venous thrombosis, intracranial hypertension syndrome (pseudotumor cerebri), acute meningeal syndrome, and uncommonly stroke due to arterial thrombosis, dissection, or aneurysm. On average, a period of approximately five to six years elapsed between the onset of the earliest non-neurologic symptoms of Behcet syndrome and the appearance of neurologic symptoms or findings.

# Pathophysiology
It is understood that Behcet disease is the result of vasculitis. It involves all sizes of blood vessels ( small, medium, and large). Arteries and veins are both involved in Behcet disease. Major mechanisms in pathogenesis of Behcet disease include environmental factors such as bacteria, viruses, and heat shock proteins (present in some bacteria and some of the bacterial HSPs share similaritis with human HSPs). Streptococcus sanguinis, streptococcus pyogenes, and mycobacterium tuberculosis produce HSPs that trigger anti HSP60 and anti HSP65 antibodies and then they target human HSPs and immune response such as uveitis in parenchymal neuro-Behcet disease, CD4+ T cells activation, secretion of cytokines and inflammation. Genes involved in the pathogenesis of Behcet disease include human leukocyte antigens, particularly HLA-B51.

# Causes
The cause of Behcet disease has not been identified.

# Differentiating Behcet's disease from other Diseases
Behcet's disease needs to be differentiated from other diseases that present with similar symptoms such as erythema nodosum and inflammatory bowel disease.

# Epidemiology and Demographics
The prevalence of Behcet disease is approximately 0.12 to 7.5 per 100,000 individuals in the United States. Behcet disease commonly affects young adults 20 to 40 years of age. Males are more commonly affected by Behcet disease than females. Behcet disease usually affects individuals of the Turkish, Asian, and Middle Eastern populations. Middle Eastern and Asian individuals are more likely to develop Behcet disease due to the increased incidence of skin pathergy and HLA-B51 antigen. The male to female ratio ranges from approximately 11 to 1 to 2 to 1. The majority of Behcet disease cases are reported along the ancient silk road (from eastern Asia to the Mediterranean).

# Risk Factors
Common risk factors in the development of Behcet disease may be occupational, environmental, genetic, and viral. Behcet's disease can affect people in any age, but the most common age is 20~30 years old. Behcet's disease is more common in Middle East and Japan then in other race. It is rare in America. Researches demonstrate that the presence of the gene HLAB51 is a risk factor for Behcet's disease.

# Screening
There is insufficient evidence to recommend routine screening for Behcet disease.

# Natural History, Complications and Prognosis
The symptoms of Behcet disease usually develop in the second to third decade of life, and start with symptoms such as uveitis, mouth sores, and skin lesions. Common complications of Behcet disease include neuro Behcet, vision loss, and aneurysm. Depending on the extent of the disease at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as good. The worst prognoses are associated with retinal vasculitis, leading to blindness; vascular aneurysm formation, with possible rupture; and neuroBehcet syndrome, which may lead to dementia despite appropriate aggressive treatment.

# Diagnosis

## Diagnostic Study of Choice
Currently, there is not a specific test to confirm the diagnosis of Behcet's disease. It is diagnosed clinically by specific patterns of symptoms and repeated outbreaks obtained by a thorough history of the patient's symptoms (outlined below). Behcet's disease is a diagnosis of exclusion, and other chronic inflammatory diseases should be evaluated for. The various inflammatory symptoms do not necessarily occur together, and they will vary in severity.

## History and Symptoms
The hallmark of Behcet disease is recurrent aphthous ulcerations, genital ulcers, and uveitis. A positive history of joint pains and skin lesions are suggestive of Behcet disease. The most common symptoms of Behcet disease include mouth sores, uveitis, joint pain, and genital sores. Less common symptoms of Behcet disease include diarrhea, abdominal pain, headache, skin lesions-red nodules, acne, joint pains, and poor balance.

## Physical Examination
Patients with Behcet disease usually appear normal. Vital signs of patients with Behcet disease are usually normal. The presence of mouth sores, genital ulcers, and vision problems on physical examination are diagnostic of Behcet disease. Skin examination of patients with Behcet disease shows erythema nodosum lesions typically occur on the extremities, especially the lower legs, but they can also be observed on the face, neck, and buttocks. The lesions are painful and resolve spontaneously, although some may ulcerate or leave hyperpigmentation. A folliculitis like rash, resembling acne vulgaris, appears on the face, neck, chest, back, and hairline of patients. Some lesions become more pustular; 24-48 hours after a sterile needle prick, some patients develop erythema with a nodule or pustule at the prick site. Ophthalmoscopic exam may be abnormal with findings of retinal vasculitis, and vaso-occlusive lesions. Uveitis of anterior and posterior chambers diagnosed with slit-lamp examination. Erythematous throat with tonsillar swelling, and exudates. Ulcers 2-15 mm in diameter, with a necrotic center and surrounding red rim. A white or yellow pseudomembrane covers the surface of the ulcer. The ulcers are typically painful, nonscarring, and found on the lips, buccal mucosa, tongue, tonsils, and larynx. Most last 7-14 days and occur in crops. Hypopyon may be observed in the anterior chamber. Genitourinary examination of patients with Behcet disease will show ulcers on the scrotum and vulva, painful and heal with scarring. Genital ulcerations tend to be deeper and larger than the oral lesions. Females can have asymptomatic ulcers. Neuromuscular examination of patients with Behcet disease will show CNS involvement in 25% of the cases. Immune-mediated meningoencephalitis predominantly involves the brainstem. Meningitis, encephalitis, focal neurological deficits, and psychiatric symptoms can be present. Irreversible dementia can occur.

## Laboratory Findings
The laboratory tests used to diagnose Behcet's disease are a pathergy test, a skin biopsy, and a lumbar puncture.

## Electrocardiogram
There are no ECG findings associated with Behcet's disease.

## X-ray
There are no x-ray findings associated with Behcet disease.

## Echocardiography  and Ultrasound
Echocardiography is useful in patients with murmurs because it is useful for diagnosing the valve vegetations and ventricular thrombi, which may occur in Behcet disease. Vascular involvement can be seen in up to 40% of patients with Behcet disease (BS) with the lower-extremity vein thrombosis (LEVT) being the most common type where ultrasonography is needed.

## CT Scan
There are no CT scan findings associated with Behcet disease. However, a CT scan may be helpful in the diagnosis of complications of Behcet disease including visualization of neurological lesions (helpful in patients with CNSinvolvement), and enlargement of ventricles or subarachnoid spaces.

## MRI
There are no MRI findings associated with Behcet disease. MRI findings of the brain may be normal even in the presence of neurologic involvement. However, a MRI may be helpful in the diagnosis of complications of Behcet disease, which include enlargement of ventricles or subarachnoid spaces, and neurological lesions present in CNS involvement.

## Other Imaging Findings
Endoscopy of the GI tract is useful for detecting gastrointestinal ulcerations in Behcet disease. A thorough eye examination and fluorescein angiography for evaluation of retinal vessels. Follow-up visits with an ophthalmologist should be scheduled at least every 6-12 months. Neuropsychologic testing may be useful with CNS involvement, revealing memory impairment or personality changes, and can be useful in monitoring neuropsychologic status.

## Other Diagnostic Studies
There are no other diagnostic studies associated with Behcet disease.

# Treatment

## Medical Therapy
Current treatment is aimed at easing the symptoms, reducing inflammation, and controlling the immune system. Anti-TNF therapy, such as infliximab, has shown promise in treating the uveitis associated with the disease. Another Anti-TNF agent, etanercept, may be useful in patients with mainly skin and mucosal symptoms. Interferon alfa-2a, azathioprine, colchicine, thalidomide, dapsone and rebamipide are among other agents that are used alternatives.

## Surgery
Surgery in Behcet's disease is performed to treat severe complications such as gastrointestinal perforations or ocular inflammatory diseases.

## Primary Prevention
There are no established measures for the primary prevention of Behcet disease.

## Secondary Prevention
There are no established measures for the secondary prevention of Behcet disease.