Behçet's disease

Meet the patient

A 28-year-old man of Turkish origin has suffered recurrent painful mouth ulcers since his teens, and each genital ulcer leaves a puckered white scar. Three weeks ago his right eye blurred; today the slit lamp shows cells, flare and a settled layer of pus in the anterior chamber, and he points to a tender red nodule on his shin. [3]

Two exam questions are now live, and you must answer both: is this Behçet's? and which organ is about to fail him? The mouth ulcers are the bait; the eye, the pulmonary artery and the brainstem are the trap. [1]

A vasculitis wearing an ulcer's mask

Behçet's is a vasculitis, not an ulcer disease — and that one reframe changes every decision. The Turkish dermatologist Hulusi Behçet described the triad of oral ulcers, genital ulcers and hypopyon uveitis in 1937; the Greek ophthalmologist Benediktos Adamantiades had reported the same constellation in 1930, hence the eponym Adamantiades-Behçet. [3]

In the 2012 Chapel Hill Consensus Conference nomenclature, Behçet's is the prototype variable-vessel vasculitis — the only named vasculitis that can inflame venules, capillaries, medium arteries and large arteries and veins alike. [6]

That breadth is the whole topic in one line: giant-cell and Takayasu are large-vessel; polyarteritis nodosa is medium-vessel; the ANCA-associated trio are small-vessel. Behçet's crosses all three lines, which is why one patient scars a scrotum and the next ruptures a pulmonary artery. [6]

Etymology for viva gold: the Silk Road eponym is literal — prevalence tracks the ancient trade route from Istanbul to Tokyo, and so does the population frequency of its genetic marker, HLA-B51. [3]

The disease is clinical, never laboratory

There is no confirmatory blood test and no pathognomonic biopsy feature. Behçet's is a diagnosis of pattern recognition plus exclusion of mimics. ANA, ANCA and rheumatoid factor are typically negative — a useful negative discriminator from lupus and the ANCA-associated vasculitides. [5]

Histology is supportive but non-specific: a neutrophilic and lymphocytic vasculitis with leukocytoclasia, not immune-complex deposition. This is why Behçet's belongs to the family of neutrophilic dermatoses alongside Sweet syndrome and pyoderma gangrenosum. [5]

[1]

Epidemiology — follow the Silk Road

Behçet's has the most striking geography in all of medicine. Prevalence tracks the ancient Silk Road and the population frequency of its genetic marker, HLA-B51. [3]

[3]

HLA-B51 is the strongest genetic association — present in 50 to 80 percent of endemic patients, conferring roughly a six-fold risk — yet it is neither necessary nor sufficient. It is supportive, not diagnostic: many healthy carriers carry it, and a sizeable minority of patients do not. Additional loci (ERAP1, IL10, IL23R) reinforce a picture of innate-immune and IL-23/Th-17 axis dysregulation. [6]

Male sex and young age at onset are the two severity predictors. Young men bear the brunt of sight-threatening eye disease, vascular events and neuro-Behçet, and they dominate the mortality statistics. In Turkey, Behçet's is a leading cause of non-traumatic blindness in young men. [6]

Pathophysiology — the two-hit model

Two hits, one disease: a genetically primed immune system over-reacts to an everyday trigger. HLA-B51 plus ERAP1, IL10 and IL23R variants lower the threshold; a microbial antigen — classically Streptococcus sanguinis — or a cross-reactive heat-shock protein pulls the trigger. [6]

The cascade runs: genetic susceptibility, then environmental trigger, then neutrophil hyperactivity (exaggerated chemotaxis and superoxide), then a Th1/Th17 skew with polyclonal B-cell activation, ending in a neutrophilic and lymphocytic vasculitis of arteries and veins. [6]

[6]

Pathergy is this hyper-reactivity made visible. A sterile needle prick raises a papule or pustule at 24 to 48 hours — an exaggerated response to minor injury, not an allergy. [5]

Why both thrombosis and aneurysm? Because the wall itself is inflamed. Endothelial injury drives coagulation and impairs fibrinolysis (thrombosis), while neutrophil-mediated destruction of the media weakens the wall (aneurysm). The thrombus is fundamentally inflammatory — which is why anticoagulation alone is inadequate and immunosuppression is central. [1]

Classification — ICBD 2014, and the oral-ulcer trap

Use ICBD 2014, score 4 or above — and forget the old rule that oral ulcers are mandatory. The 1990 International Study Group criteria made recurrent oral ulceration compulsory; the 2014 ICBD, validated across 27 countries, dropped that requirement and up-weighted the eye and genitals. [7]

In the validation cohort the ICBD achieved sensitivity 94.8 percent and specificity 90.5 percent, beating the 1990 criteria on both. [7]

Clinical presentation — the company the ulcer keeps

The tempo is relapsing-remitting, the mouth ulcer is almost always first, and the danger is always downstream. Oral ulcers open the show; the eye, the vasculature and the brain arrive later, sometimes years apart. [3]

Mucocutaneous — present in nearly all

Recurrent oral aphthae occur in 97 to 99 percent and are usually the first sign: painful, multiple, on the lips, buccal mucosa, tongue and palate. Minor aphthae heal in one to three weeks without scarring; major aphthae are larger and scar. In isolation they are indistinguishable from ordinary aphthous stomatitis — it is the company they keep that defines Behçet's. [4]

Genital ulcers occur in 80 to 90 percent, sit on the scrotum or vulva, and — the high-yield discriminator — heal with scarring. Mouth ulcers fade; genital ulcers mark. [6]

[6]

The discriminator line: oral aphthae heal clean, genital ulcers leave a scar. One bedside question resolves it. [1]

Skin lesions affect 60 to 90 percent and take three forms: tender erythema-nodosum-like nodules on the shins, acneiform and papulopustular eruptions on trunk and face, and a positive pathergy reaction. An adolescent-pattern acne in a young adult of Silk-Road origin should make you think Behçet's before you reach for a retinoid. [1]

Ocular — about half, and the organ you cannot afford to miss

Any new eye symptom in a Behçet patient is an emergency. Permanent retinal damage accrues with each untreated attack, and early anti-TNF has cut the historical blindness rate. [6]

Anterior disease gives cells and flare and the once-signature hypopyon — now uncommon because we treat earlier. Posterior disease gives retinal vasculitis with sheathing, occlusion, cotton-wool spots and haemorrhages; recurrent occlusive vasculitis ends in neovascularisation and irreversible visual loss. [6]

The discriminator from HLA-B27 acute anterior uveitis: Behçet uveitis is typically bilateral, recurrent and panuveal, and it involves the posterior segment. [1]

Vascular — about a quarter, and the one that kills

Behçet's is one of the few conditions that causes both venous thrombosis and arterial aneurysm. Venous disease dominates (DVT, cerebral venous sinus thrombosis, Budd-Chiari); arterial disease is rarer but deadlier — pulmonary artery aneurysm presents with haemoptysis and is a leading cause of death. [6]

Neurological — 5 to 10 percent, two faces

Neuro-Behçet has two faces with opposite prognoses — name both at viva. [2]

[2]

A headache in a Behçet patient is never "just a headache" until cerebral venous sinus thrombosis and parenchymal disease are excluded on MRI brain with venography. The brainstem is the classic parenchymal site — a young Silk-Road man with a brainstem stroke syndrome should prompt the diagnosis even before the mouth ulcers are volunteered. [2]

The rest of the multisystem picture

Arthritis is non-erosive, asymmetric, oligoarticular (knees and ankles) and responds to colchicine or NSAIDs. [1] Gastrointestinal ileocaecal ulceration mimics Crohn — deep punched-out ulcers rather than transmural granulomatous inflammation — and may perforate or bleed. [6]

[6]

Epididymitis, cardiac involvement (pericarditis, myocarditis, intracardiac thrombus) and renal AA amyloidosis from chronic inflammation round out the multisystem picture. [6]

Differential — name the mimic and the separator

The mimic that costs the most marks is Crohn disease, because both produce oral aphthae, genital fissures and ileocaecal disease. [1]

[1]

The discriminator line: Behçet gives panuveitis and retinal vasculitis plus pathergy; Crohn gives anterior uveitis and granulomas. Hold both halves of that sentence and the viva mark is yours. [6]

Bedside assessment — three questions

The focused assessment answers three questions: is the eye involved, is there large-vessel disease, is the brain involved? [1]

History establishes ulcer onset, frequency and whether genital ulcers scar, eye symptoms, skin lesions, any thrombosis, headache or weakness, abdominal pain and family origin. Examination covers the oral cavity (ulcers at every stage), the genitalia (active ulcers and scars), the skin, a mandatory slit-lamp examination, the joints, peripheral pulses and a neurological screen. [3]

The pathergy test is a sterile oblique prick with a 20-gauge needle into the forearm, read at 24 to 48 hours. A papule or pustule 2 mm or larger is positive. Specificity is high in endemic populations; sensitivity is geography-dependent — over 60 percent in Turkey and Japan, under 20 percent in Northern Europe — so a negative test never excludes the disease. [5]

Investigations — support, stage, exclude

There is no confirmatory test. Investigations support the pattern, stage the organ involvement and exclude the mimics. [1]

Bloods show raised ESR and CRP in active disease and a mild anaemia of chronic disease; ANA, dsDNA and ANCA are usually negative (useful negative discriminator). HLA-B51 is supportive in the right ethnic context, not diagnostic. [3]

Slit-lamp and fundoscopy are non-negotiable at baseline and every flare; fluorescein angiography defines retinal vasculitis and OCT quantifies macular oedema. [6]

Imaging is symptom-directed: CT or MR angiography for suspected pulmonary artery aneurysm or large-vessel disease, Doppler ultrasound for DVT, and MRI brain with venography for suspected neuro-Behçet. [2]

A mimics panel closes the work-up: viral swabs and PCR for herpes simplex, serology for syphilis and HIV, and — when the ileocaecal picture dominates — faecal calprotectin and colonoscopy with biopsy to separate Behçet enteropathy from Crohn. [6]

Management — the four emergencies first

Most Behçet presentations are subacute, but four are time-critical and decide whether the patient keeps their sight or their life. [1]

[1]

The unifying principle: corticosteroids put out the fire, immunosuppression keeps it out. A short course of high-dose steroid is layered onto a slower-acting steroid-sparing agent, and the steroid is tapered as the latter takes hold. [8]

Management — treat the phenotype, not the label

Treatment is organ-based, and the 2018 EULAR recommendations formalise exactly that. A patient with mouth ulcers and a patient with a pulmonary artery aneurysm are prognostically different diseases, and they are treated differently. [8]

Mucocutaneous disease — colchicine first

Colchicine is first-line for oral and genital ulcers and erythema-nodosum-like lesions, typically 0.5 mg twice daily. Topical corticosteroids (triamcinolone dental paste) and topical anaesthetics soothe individual ulcers. [4]

For refractory mucocutaneous disease, apremilast (a PDE4 inhibitor, 30 mg twice daily) reduced oral ulcers in a phase 2 trial; thalidomide (50–150 mg daily) works but is teratogenic and neurotoxic; dapsone and azathioprine are alternatives. [9]

Ocular disease — escalate early

Azathioprine plus corticosteroids is the backbone (check TPMT first). For sight-threatening posterior disease or refractory cases, anti-TNF — infliximab 5 mg/kg or adalimumab 40 mg subcutaneously — is the treatment of choice and has transformed the ocular prognosis. [8]

Articular disease

Colchicine and NSAIDs are first-line for the non-erosive arthritis; persistent disease escalates to azathioprine, interferon-alpha or anti-TNF. [1]

Neuro-Behçet — and the ciclosporin ban

High-dose corticosteroids plus a steroid-sparing agent is standard — azathioprine for maintenance, infliximab for refractory disease, cyclophosphamide for severe disease. [2]

Vascular disease — immunosuppression is central

Because the thrombus is inflammation-driven, immunosuppression is central — corticosteroids plus azathioprine, or cyclophosphamide for severe large-vessel or pulmonary artery aneurysm disease. The role of anticoagulation is controversial: it may help extensive DVT but bleeds dangerously when a pulmonary artery aneurysm is present, and Behçet thrombi rarely embolise anyway. [6]

Gastrointestinal disease

Corticosteroids plus 5-aminosalicylic acid agents or azathioprine are first-line; surgery for perforation or refractory bleeding; anti-TNF for refractory disease. [6]

[3] [8] [1]

Specific subtypes and scenarios

Ocular Behçet is the prototype of sight-threatening disease: posterior-segment involvement (retinal vasculitis, macular oedema) drives permanent visual loss, and early anti-TNF has cut the historical blindness rate. [6]

Vascular Behçet is dominated by the pulmonary artery aneurysm — the single most feared lesion, presenting with haemoptysis, prone to catastrophic rupture, treated with IV corticosteroids plus cyclophosphamide and embolisation or surgery for high-risk lesions. [6]

Paediatric Behçet often masquerades as isolated recurrent aphthous stomatitis for years before the full phenotype declares itself; a family history and HLA-B51 positivity should lower the referral threshold. MAGIC syndrome (Mouth And Genital ulcers with Inflamed Cartilage) is the recognised overlap with relapsing polychondritis. [3]

Complications — the preventable list

The complications cluster around vision, the lung vasculature and the brain. [1]

[6]

How Behçet patients come to harm (the preventable list): [1]

• A young man losing sight because nobody slit-lamped a quiet eye during a flare. [6]
• A haemoptysis read as infection when the cause was a pulmonary artery aneurysm. [6]
• A thrombosis anticoagulated without immunosuppression, so the wall stayed inflamed and the clot grew. [6]
• A neuro-Behçet given ciclosporin, which worsened the central nervous system disease. [2]
• Oral ulcers alone labelled Behçet's without excluding Crohn, herpes or syphilis. [1]

Prognosis and disposition

Disease activity tends to abate with age — a much-tested pearl — but young men with vascular or neurological disease keep a measurably reduced life expectancy. Pulmonary artery aneurysm rupture, fatal neuro-Behçet and catastrophic large-vessel arterial disease are the principal causes of death. [6]

Isolated mucocutaneous disease carries a near-normal life expectancy. The corollary examiners reward: prognosis is set by which organs are involved, not by the disease label. [6]

Management is lifelong and multidisciplinary — rheumatology leads, ophthalmology is essential and frequent, with dermatology, neurology, gastroenterology and vascular surgery added by phenotype. Patients must learn to recognise flares — eye symptoms, headache, haemoptysis — and seek early review. [1]

Special populations

Pregnancy needs coordinated obstetric and rheumatology care: colchicine may be continued where benefit justifies it, azathioprine is acceptable, and thalidomide, methotrexate and ciclosporin are avoided. Disease may flare postpartum. [8]

Paediatric disease smoulders as isolated aphthosis for years; colchicine is dosed by weight. Late-onset disease (over 40) runs milder with fewer severe ocular and vascular events. [1]

Geography changes how the criteria perform: pathergy is positive in most Turkish and Japanese patients but in fewer than a fifth of Northern Europeans, so a patient in London may meet ICBD without the pathergy point expected in Istanbul. [5]

Evidence and regional differences

The two evidence pillars are the ICBD 2014 criteria and the EULAR 2018 management recommendations. [1]

[1]

The evidence base is moderate rather than large — Behçet's rarity outside endemic regions means most treatment data come from cohorts and a modest number of randomised trials. Anti-TNF evidence for sight-threatening disease is strong despite resting largely on uncontrolled cohorts. [8]

Where the evidence is weak: anticoagulation for Behçet thrombosis remains the longest-standing controversy — no randomised evidence guides it, and practice splits between immunosuppression alone (Japan) and immunosuppression plus anticoagulation for extensive DVT (Europe). Interleukin-1 and interleukin-17 blockade shows promise but has not displaced anti-TNF for ocular disease. [6]

Exam pearls

[1]

Exam application bank (NEET-PG and INICET)

One-line answer

Behçet's disease is a relapsing-remitting multisystem vasculitis affecting both veins and arteries (a variable-vessel vasculitis), presenting with recurrent oral aphthous ulcers, genital ulcers that scar, ocular inflammation and skin lesions, concentrated along the Silk Road and associated with HLA-B51. Diagnosis is clinical using the ICBD 2014 criteria (score 4 or above). Colchicine is first-line for mucocutaneous disease; anti-TNF for sight-threatening or refractory disease; ciclosporin is avoided in neuro-Behçet. [3]

Worked stems (answer without another resource)

Stem 1 — Classic presentation. Map symptoms to mechanism; name the first investigation and first treatment step with dose and route if drug therapy is standard. [1]

Stem 2 — Unstable or complicated. List red flags that force immediate resuscitation, theatre, ICU, antidote or reperfusion — and what you do in the first 15 minutes. [1]

Stem 3 — Atypical group. Elderly, pregnancy, child or immunocompromised: how presentation and thresholds change. [1]

Stem 4 — Differential trap. Name the three closest mimics and one discriminator for each. [1]

Stem 5 — Disposition. Who goes home with safety-netting, who is admitted, who needs HDU, ICU or theatre, and what follow-up is mandatory. [1]

Rapid viva checklist

1. Definition and classification
2. Pathophysiology chain
3. Bedside signs and criteria
4. Score with exact components
5. Emergency bundle
6. Definitive therapy with doses
7. Complications of disease and of treatment
8. Special populations
9. Guideline or trial name if classic
10. Three exam traps

Coverage self-check

If you cannot answer any stem above from this page alone, re-read the matching section — the page is intended to be self-sufficient for final-prof and NEET-PG/INICET questions on Behçet's disease.

Ward-round test — three stems, thirty seconds each

Stem 1 — the man from the top of the topic (answer)

The 28-year-old with oral and scrotal ulcers, a hypopyon and a shin nodule. What is the diagnosis, and what do you do in the next hour? Model: This is Behçet's disease — recurrent oral aphthae, genital ulcers that scar, panuveitis with hypopyon, and erythema-nodosum-like skin lesions in a Silk-Road patient. Apply the ICBD 2014 criteria (ocular 2, genital aphthosis 2, oral aphthosis 2, skin 1 — already 7, well above 4). The eye makes this an emergency: urgent ophthalmology, slit-lamp and fundoscopy with fluorescein angiography, then high-dose corticosteroid (IV methylprednisolone 0.5–1 g daily for 3 days) layered onto a steroid-sparing agent (azathioprine after a TPMT check), with anti-TNF held in reserve for sight-threatening posterior disease. Start colchicine 0.5 mg twice daily for the mucocutaneous disease. Screen for HLA-B51, exclude mimics (Crohn, herpes, syphilis) and arrange multidisciplinary follow-up. [3]

Stem 2 — the haemoptysis that is not a PE (answer)

A 32-year-old man with known Behçet's presents with haemoptysis and a normal ECG. The registrar wants to anticoagulate for a presumed pulmonary embolism. What is the trap? Model: In Behçet's the breathless patient is far more likely to have in-situ pulmonary artery thrombosis or a pulmonary artery aneurysm than an embolus, because Behçet thrombi are adherent and rarely embolise. The correct move is urgent CT angiography to define a pulmonary artery aneurysm, then IV corticosteroids plus cyclophosphamide (immunosuppression is central, because the vessel wall is inflamed), with embolisation or surgery for high-rupture-risk lesions. Blind anticoagulation in the presence of an aneurysm risks catastrophic bleeding — the clot is inflammation-driven, not embolic. [6]

Stem 3 — the headache that is never just a headache (answer)

A 26-year-old man with Behçet's has a three-day headache, blurred vision and papilloedema. What is the diagnosis, and which drug is now contraindicated? Model: Papilloedema and headache point to cerebral venous sinus thrombosis (the better-prognosis form of neuro-Behçet) — confirm with MRI brain and MR venography, exclude haemorrhage, then anticoagulate plus corticosteroids. The contraindicated drug is ciclosporin — it is neurotoxic in Behçet's and can precipitate or worsen central nervous system disease. If the MRI instead shows a brainstem or thalamocapsular lesion, that is parenchymal neuro-Behçet (poor prognosis), treated with high-dose corticosteroids plus azathioprine or anti-TNF — still no ciclosporin. [2]

The mantra: mouth ulcers are the bait; slit-lamp the eye, image the lung and brain — and never reach for ciclosporin when the brain is involved. [1][8]

References

1. [1]Pérez-Garza DM, Chavez-Alvarez S, Ocampo-Candiani J, et al. Erythema Nodosum: A Practical Approach and Diagnostic Algorithm Am J Clin Dermatol, 2021.PMID 33683567
2. [2]Belfeki N, Ghriss N, Fourati M, et al. Neuro-Behçet's disease: A review Rev Med Interne, 2024.PMID 38937151
3. [3]Fazaa A, Makhlouf Y, Ben Massoud F, et al. Behçet disease: epidemiology, classification criteria and treatment modalities Expert Rev Clin Immunol, 2024.PMID 39101633
4. [4]Manfredini M, Guida S, Giovani M, et al. Recurrent Aphthous Stomatitis: Treatment and Management Dermatol Pract Concept, 2021.PMID 34631263
5. [5]Nelson CA, Stephen S, Ashchyan HJ, et al. Neutrophilic dermatoses: Pathogenesis, Sweet syndrome, neutrophilic eccrine hidradenitis, and Behçet disease J Am Acad Dermatol, 2018.PMID 29653210
6. [6]Lavalle S, Caruso S, Foti R, et al. Behçet's Disease, Pathogenesis, Clinical Features, and Treatment Approaches: A Comprehensive Review Medicina (Kaunas), 2024.PMID 38674208
7. [7]International Team for the Revision of the International Criteria for Behçet's Disease (ITR-ICBD). The International Criteria for Behçet's Disease (ICBD): a collaborative study of 27 countries on the sensitivity and specificity of the new criteria J Eur Acad Dermatol Venereol, 2014.PMID 23441863
8. [8]Hatemi G, Christensen R, Bang D, et al. 2018 update of the EULAR recommendations for the management of Behçet's syndrome Ann Rheum Dis, 2018.PMID 29625968
9. [9]Hatemi G, Melikoglu M, Tunc R, et al. Apremilast for Behçet's syndrome--a phase 2, placebo-controlled study N Engl J Med, 2015.PMID 25875256