Polyarteritis nodosa

Gastrointestinal (GI) involvement in polyarteritis nodosa (PAN) usually manifests as nonspecific symptoms such as abdominal pain, nausea, and/or vomiting, with or without obvious GI bleeding (blood in the stools).^[1] Abdominal discomfort may be intermittent or continuous and may be most prominent after meals.^[2] Weight loss may follow due to decreased food intake and/or malabsorption.^[2]

In some cases, symptoms may depend on the exact location of the affected part of the GI tract. For example, vasculitis affecting the liver or gallbladder may cause right upper quadrant pain.^[3]

More serious complications of PAN involving the GI tract are rare but include bowel infarction (obstruction of blood) and perforation, cholecystitis, hepatic infarction, or pancreatic infarction.^[1]

The exact cause of polyarteritis nodosa (PAN) is not known, and in most cases, no predisposing cause has been found (it is idiopathic). Many scientists believe that it is an autoimmune disease. Research has suggested that an abnormal immune response to an initial infection may trigger the development of PAN.^[4] However, the reasons that many smaller arteries and capillaries are spared is not understood.^[2]

Hepatitis B virus (HBV), hepatitis C, and hairy cell leukemia have been associated with some cases of PAN. In one report from France, HBV accounted for a third of the cases of PAN. HBV-related PAN typically occurs within four months after the onset of HBV infection.^[2] PAN has also been seen in drug abusers (particularly those using amphetamines). It has also appeared to occur as an allergic reaction to some drugs and vaccines.^[4]

The specific symptoms of PAN are due to ischemia or infarction of tissues and organs. Thickening of the walls of affected vessels causes narrowing of the inside of the vessels, reducing blood flow and predisposing to blood clots in affected vessels.^[2]

Polyarteritis nodosa (PAN) has sometimes been referred to as a "collagen disease" or a "collagen vascular disease."^[5][6][7] Historically, the term "collagen vascular disease" has been used to describe similar autoimmune disorders associated with inflammation of the connective tissues (including the arteries). Connective tissues are made up of collagen fibers, in addition to other materials. However, now that we have names for these individual disorders, the term is not used as frequently for these disorders.^[5] Additionally, the term "collagen disease" has more recently been used to describe diseases caused by defects in collagen (eg, Ehlers-Danlos syndrome), rather than diseases affecting structures made of collagen. To our knowledge, there is not currently evidence that PAN is due to a defect in collagen. Besides PAN, other disorders that have been considered collagen vascular diseases include ankylosing spondylitis, dermatomyositis, psoriatic arthritis, rheumatoid arthritis, scleroderma, and systemic lupus erythematosus.^[6]

Polyarteritis nodosa (PAN) is a rare disease, with an incidence of about 3 to 4.5 cases per 100,000 people annually in the United States (about 1 in 22,000 to 1 in 33,000 people). Internationally, the annual estimated incidence of PAN ranges from 1.6 cases per million in south Sweden, for example, to 30.7 cases per million adults in Paris.^[1]

PAN affects men more frequently than women. While it has been diagnosed in people of every age, it predominantly occurs in people between the ages of 45-65 years.^[1]