The most common ocular complications include macular edema, intraocular pressure rise, cataracts, and optic atrophy. Less commonly, patients develop branch retinal vein occlusions (Fig. 17.3), iris atrophy, macular degeneration with pigment epithelial changes, epiretinal membrane formation, and retinal neovascularization. Neovascularization can result in vitreous hemorrhage or tractional retinal detachment [1]. Fluorescein angiography (FA) can be used to monitor vasculitis as well as look for neovascularization. Peripheral retinal capillary leakage on FA can be seen in asymptomatic patients and can indicate inadequate therapeutic response.

As a multisystem vasculitis, ABD causes symptoms throughout the body. Patients often have oral aphthous ulcers; these are painful, last up to 14 days and present an average of seven and a half years prior to diagnosis [1]. These ulcers are covered by white to yellow pseudomembranes, surrounded by an erythematous halo, and occur on mucous membranes [11]. Genital ulcers are also common. These ulcers have sharp borders with a fibrin-covered floor and surrounding erythema. They most commonly occur on the scrotum and inguinal area in men and vulva and inguinal area in women [11]. Two common skin manifestations are erythema nodosum and pseudofolliculitis. Patients will classically have a positive pathergy test, which is the formation of an indurated erythematous papule 24–48 h after intracutaneous prick with a needle on the forearm [1]. Patients can have transient arthralgias, neurologic symptoms ranging from hemiparesis to behavioral changes, vascular thrombosis, and GI symptoms including colitis or ulceration. Cardiac angina or infarction, pulmonary manifestations, epididymitis, orchitis, and renal manifestations are rare but have been reported [1].

Formal diagnosis is based on two sets of guidelines: the International Study Group Classification from 1990 and the revised criteria by the Behcet’s Disease Research Committee of Japan from 2003 [7, 10]. The International Study Group Classification is used in most countries in the world. Because a subset of patients with ABD will have ocular involvement as their initial manifestation of disease, ophthalmologists should be aware of these diagnostic guidelines and ask uveitis patients about systemic symptoms of ABD. Patients with suggestive systemic symptoms should be referred to a rheumatologist for formal diagnosis. HLA-B51 testing is indicated when there are systemic symptoms suggestive of ABD. In this context, a positive HLA-B51 result can help fulfill diagnostic criteria for the disease. Since a significant proportion of patients with ABD do not have the HLA-B51 allele, a negative result does not necessarily exclude the diagnosis.

The International Behcet’s Study Group Classification (IBSGC) requires the presence of recurrent (at least three times in a one-year period) oral ulcers to make a diagnosis, with at least two of the following: recurrent genital ulcers, skin lesions, eye lesions, or a positive pathergy test (Table 17.1) [3]. This classification has been validated in several populations and is 91 % sensitive and 96 % specific [11].

The Japanese Criteria (JC) classifies recurrent aphthous ulcers on the oral mucosa, skin lesions, eye lesions, and genital ulcers as main symptoms. It classifies arthritis, gastrointestinal lesions characterized by ileocecal ulcers, epidydimitis, vascular lesions, and central nervous system symptoms as additional symptoms. A “complete” diagnosis requires four main symptoms. An “incomplete” diagnosis requires three main symptoms, or two main with two additional symptoms, or a typical ocular lesion with a main symptom, or a typical ocular lesion with two additional symptoms. These revised criteria also allow laboratory and clinical testing to contribute to the diagnosis. They include pathergy testing and prick testing for sensitivity to dead Streptococci (Table 17.2) [7].