Behçet disease is an inflammatory condition that affects many parts of the body. The health problems associated with Behçet disease result from widespread inflammation of blood vessels (vasculitis). This inflammation most commonly affects small blood vessels in the mouth, genitals, skin, and eyes.\n\nPainful mouth sores called aphthous ulcers are usually the first sign of Behçet disease. These sores can occur on the lips, tongue, inside the cheeks, the roof of the mouth, the throat, and the tonsils. The ulcers look like common canker sores, and they typically heal within one to two weeks. About 75 percent of all people with Behçet disease develop similar ulcers on the genitals. These ulcers occur most frequently on the scrotum in men and on the labia in women.\n\nBehçet disease can also cause painful bumps and sores on the skin. Most affected individuals develop pus-filled bumps that resemble acne. These bumps can occur anywhere on the body. Some affected people also have red, tender nodules called erythema nodosum. These nodules usually develop on the legs but can also occur on the arms, face, and neck.\n\nAn inflammation of the eye called uveitis is found in more than half of people with Behçet disease. Eye problems are more common in younger people with the disease and affect men more often than women. Uveitis can result in blurry vision and an extreme sensitivity to light (photophobia). Rarely, inflammation can also cause eye pain and redness. If untreated, the eye problems associated with Behçet disease can lead to blindness.\n\nJoint involvement is also common in Behçet disease. Often this affects one joint at a time, with each affected joint becoming swollen and painful and then getting better.\n\nLess commonly, Behçet disease can affect the brain and spinal cord (central nervous system), gastrointestinal tract, large blood vessels, heart, lungs, and kidneys. Central nervous system abnormalities can lead to headaches, confusion, personality changes, memory loss, impaired speech, and problems with balance and movement. Involvement of the gastrointestinal tract can lead to a hole in the wall of the intestine (intestinal perforation), which can cause serious infection and may be life-threatening.\n\nThe signs and symptoms of Behçet disease usually begin in a person's twenties or thirties, although they can appear at any age. Some affected people have relatively mild symptoms that are limited to sores in the mouth and on the genitals. Others have more severe symptoms affecting various parts of the body, including the eyes and the vital organs. The features of Behçet disease typically come and go over a period of months or years. In most affected individuals, the health problems associated with this disorder improve with age.

Heterozygous protein C deficiency is characterized by recurrent venous thrombosis. However, many adults with heterozygous disease may be asymptomatic (Millar et al., 2000). Individuals with decreased amounts of protein C are classically referred to as having type I deficiency and those with normal amounts of a functionally defective protein as having type II deficiency (Bertina et al., 1984). Acquired protein C deficiency is a clinically similar disorder caused by development of an antibody against protein C. Clouse and Comp (1986) reviewed the structural and functional properties of protein C and discussed both hereditary and acquired deficiency of protein C.

Autosomal recessive protein C deficiency resulting from homozygous or compound heterozygous PROC mutations is a thrombotic condition that can manifest as a severe neonatal disorder or as a milder disorder with late-onset thrombophilia (Millar et al., 2000).

Heterozygous protein S deficiency, like protein C deficiency (176860), is characterized by recurrent venous thrombosis. Bertina (1990) classified protein S deficiency into 3 clinical subtypes based on laboratory findings. Type I refers to deficiency of both free and total protein S as well as decreased protein S activity; type II shows normal plasma values, but decreased protein S activity; and type III shows decreased free protein S levels and activity, but normal total protein S levels. Approximately 40% of protein S circulates as a free active form, whereas the remaining 60% circulates as an inactive form bound to C4BPA (120830). Zoller et al. (1995) observed coexistence of type I and type III PROS1-deficient phenotypes within a single family and determined that the subtypes are allelic. Under normal conditions, the concentration of protein S exceeds that of C4BPA by approximately 30 to 40%. Thus, free protein S is the molar surplus of protein S over C4BPA. Mild protein S deficiency will thus present with selective deficiency of free protein S, whereas more pronounced protein S deficiency will also decrease the complexed protein S and consequently the total protein S level. These findings explained why assays for free protein S have a higher predictive value for protein S deficiency. See also autosomal recessive thrombophilia due to protein S deficiency (THPH6; 614514), which is a more severe disorder.

Autosomal recessive thrombophilia due to protein S deficiency is a very rare and severe hematologic disorder resulting in thrombosis and secondary hemorrhage usually beginning in early infancy. Some affected individuals develop neonatal purpura fulminans, multifocal thrombosis, or intracranial hemorrhage (Pung-amritt et al., 1999; Fischer et al., 2010), whereas others have recurrent thromboses later in childhood (Comp et al., 1984). See also autosomal dominant thrombophilia due to protein S deficiency (THPH5; 612336), a less severe disorder caused by heterozygous mutation in the PROS1 gene.