Familial Mediterranean Fever (FMF)
FMF is the most common auto-inflammatory syndrome, with more than 100,000 patients worldwide. It is almost exclusively found in people who come from countries around the Mediterranean sea. The highest rate is found among Armenians, Turks, Arabs and Jews of Sephardic origin. The disease is extremely rare in autochthonous Belgians.
Signs and symptoms
The symptoms of FMF have a paroxysmal character. Typically takes an attack will last for 12 hours to 3-4 days. Attacks of FMF are characterized by fever accompanied by signs of serositis (inflammation of the tissue that lines the internal organs). Abdominal pain, as an expression of sterile peritonitis occurs in almost all patients. In addition, one third of patients have recurrent pleurisy, (pleura inflammation). In 25-40% of the patients, the fever attacks are associated with arthritis (joint inflammation), in particular of the knees, wrists, and ankles.
In 1997, the gene that causes FMF was discovered. It is located on the short arm of chromosome 16. Several mutations are known to cause disease. The gene encodes a protein which is called pyrin. The exact mechanism how mutation in pyrin leads to recurrent inflammation remain to be elucidated. Pyrin seems to play an important role in the inflammatory response of the innate immune system.
FMF is a clinical diagnosis. That is to say that the diagnosis can be made in the majority of patients on the basis of the signs and symptoms in combination with the ethnic origin. The diagnosis can be confirmed by genetic analysis of the pyrin gene (MEFV).
Colchicine is the treatment of choice for FMF. In most patients, it is very effective in the prevention of attacks. It is even so effective that the prevention of attack by colchicine is regarded as one of the clinical criteria for diagnosis. Only a small proportion of the patients do not respond to treatment with colchicine or are unable to tolerate this treatment. In these patients, IL1-blocking drugs are very effective.