Section 25. Special Subjects

Chapter 305. Familial Mediterranean Fever

Topic: Familial Mediterranean Fever

Familial Mediterranean Fever

Familial Mediterranean fever (familial paroxysmal peritonitis) is an inherited disorder characterized by episodes of high fever together with abdominal pain or, less commonly, chest pain, joint pain, or a rash.

Familial Mediterranean fever occurs most commonly among people of Mediterranean origin (for example, Sephardic Jews, Arabs, Armenians, and Turks). However, in the United States, about 50% of people with familial Mediterranean fever have no known family history of the disorder.

Familial Mediterranean fever is an inherited disorder caused by an abnormal recessive gene (see Section 1, Chapter 2). The abnormal gene results in the production of a defective form of pyrin, a protein that regulates inflammation. Some people with familial Mediterranean fever who do not receive proper treatment develop amyloidosis, in which an unusually shaped protein called amyloid is deposited in many organs and tissues, impairing their function (see Section 25, Chapter 304).

Symptoms and Diagnosis

Symptoms usually begin between the ages of 5 and 15. The person experiences irregularly occurring attacks of abdominal pain accompanied by fever as high as 104° F. The painful attacks usually last 24 to 72 hours but occasionally may last as long as a week. Attacks may occur as often as twice a week or as seldom as once a year. The severity and frequency of the attacks tend to decrease with age and during pregnancy. Sometimes the attacks stop completely for a number of years, only to resume later.

Recurring abdominal pain occurs in 95% of people with familial Mediterranean fever. The pain is caused by inflammation of the lining of the abdominal cavity (peritonitis). The pain usually starts in one part of the abdomen and then spreads throughout the entire abdomen. The severity of the pain may vary with each attack. Chest pain occurs in fewer than 50% of people with familial Mediterranean fever in the United States. Chest pain is caused by inflammation of the membranes surrounding the lungs (pleuritis) or, in extremely rare cases, by inflammation of the sac surrounding the heart (pericarditis). Inflammation of the large joints (arthritis), such as the knees, occurs in about 10% of people with familial Mediterranean fever in the United States; the percentage is higher in other parts of the world, such as North Africa. Also comparatively rare in the United States is a painful red rash that usually appears near the ankles. People in whom amyloidosis affects the kidneys may experience fluid retention, weakness, and loss of appetite.

A doctor usually makes a diagnosis based on the typical symptoms. However, the abdominal pain of familial Mediterranean fever is virtually indistinguishable from that of other abdominal emergencies, particularly a ruptured appendix. Thus, some people with this condition undergo urgent surgery before the correct diagnosis is made. No routine laboratory test is by itself diagnostic, but such tests can be useful in excluding other conditions. Blood tests to determine a hereditary component can aid in making the diagnosis.

Prognosis, Prevention, and Treatment

Despite the severity of symptoms during attacks, people rapidly recover and remain free of illness until their next attack. However, if the disorder is not treated, some people develop kidney damage and eventually kidney failure because of amyloid deposited in the kidneys.

The daily use of colchicine, taken by mouth, eliminates or markedly reduces the number of attacks of pain in about 85% of people and virtually eliminates the risk of kidney failure due to amyloidosis. For people with infrequent attacks, colchicine can be withheld until symptoms first occur but then must be taken promptly.

Although mild analgesics, such as nonsteroidal anti-inflammatory drugs (NSAIDs) (see Section 6, Chapter 78), may relieve pain sufficiently, opioids, such as meperidine, are usually needed.