Familial Mediterranean fever (FMF) is a genetic autoinflammatory disorder that causes recurrent fevers and painful inflammation of your abdomen, chest and joints.
FMF is an inherited disorder that usually occurs in people of Mediterranean origin — including those of Jewish, Arab, Armenian, Turkish, North African, Greek or Italian ancestry. But it can affect people in any ethnic group.
FMF is typically diagnosed during childhood. While there's no cure for this disorder, you may be able to relieve or even prevent signs and symptoms of FMF by following your treatment plan.
Signs and symptoms of familial Mediterranean fever usually begin during childhood. They occur in bouts called attacks that last 1-3 days. Arthritic attacks may last for weeks or months.
Signs and symptoms of FMF attacks vary, but can include:
- Abdominal pain
- Chest pain, which can make it hard to breathe deeply
- Painful, swollen joints, usually in the knees, ankles and hips
- A red rash on your legs, especially below your knees
- Muscle aches
- A swollen, tender scrotum
The attacks generally resolve spontaneously after a few days. Between attacks, you'll likely feel back to your typical health. Symptom-free periods may be as short as a few days or as long as several years.
In some people, the first sign of FMF is amyloidosis. With amyloidosis, the protein amyloid A, which is not typically found in the body, builds up in organs ⸺ especially the kidneys ⸺ causing inflammation and interfering with their function.
When to see a doctor
See your health care provider if you or your child has a sudden fever accompanied by pain in the abdomen, chest and joints.
Familial Mediterranean fever is caused by a gene change (mutation) that's passed from parents to children. The gene change affects the function of an immune system protein called pyrin, causing problems in regulating inflammation in the body.
In people with FMF, change occurs in a gene called MEFV. Many different changes in MEFV are linked to FMF. Some changes may cause very severe cases, while others may result in milder signs and symptoms.
It's unclear what exactly triggers attacks, but they may occur with emotional stress, menstruation, exposure to cold, and physical stress such as illness or injury.
Factors that may increase the risk of familial Mediterranean fever include:
- Family history of the disorder. If you have a family history of FMF, you have a higher risk of the disorder.
- Mediterranean ancestry. If your family can trace its history to the Mediterranean region, your risk of the disorder may be increased. FMF can affect people in any ethnic group, but it may be more likely in people of Jewish, Arab, Armenian, Turkish, North African, Greek or Italian descent.
Complications can occur if familial Mediterranean fever isn't treated. Inflammation can lead to complications such as:
- Amyloidosis. During attacks of FMF, your body may produce a protein called amyloid A, not typically found in the body. Buildup of this protein causes inflammation, which can cause organ damage.
- Kidney damage. Amyloidosis can damage the kidneys, causing nephrotic syndrome. Nephrotic syndrome occurs when your kidneys' filtering systems (glomeruli) are damaged. People with nephrotic syndrome may lose large amounts of protein in their urine. Nephrotic syndrome can lead to blood clots in your kidneys (renal vein thrombosis) or kidney failure.
- Joint pain. Arthritis is common in people with FMF. The most commonly affected joints are the knees, ankles and hips.
- Infertility. Untreated inflammation caused by FMF may affect the reproductive organs, causing infertility.
- Other complications. These can include inflammation in the heart, lungs, spleen, brain and superficial veins.