Familial Mediterranean fever (FMF) is an inherited disorder of unknown etiology, characterized by recurrent episodes of fever, peritonitis and/or pleuritis.

Fever is the cardinal manifestation of FMF and is present in most attacks accompanied by abdominal pain.

Another clinical manifestation in patients with FMF is exertional muscle pain, usually in the thigh, which appears even after minor exercise or physical activity in young patients with generally good health (other than FMF) and in good physical condition. Some patients also complain of ankle edema after relatively minor physical activity, which subsides after a night rest. Although these manifestations are quite common in FMF patients and form part of the minor criteria for the diagnosis, the etiopathogenesis has not been examined.

The purpose of the suggested study is to evaluate and characterize the anatomical and biochemical changes in the muscles of the thigh and in the ankle triggered by physical activity in FMF patients complaining of exertional lower leg myalgias and edema after minor physical exercise.

Inclusion Criteria:

1. Fulfilling the Tel Hashomer criteria for the diagnosis of FMF [5].
2. Suffering from episodes of exertional leg pain and or exertional ankle edema
3. 18-45 years old
4. On a stable (≥ 2 weeks) dose of oral colchicine therapy
5. Non-smokers

Exclusion Criteria:

1. with known peripheral vascular disease (PVD) and/or multiple risk factors for PVD (such as diabetes, hypertension, hyperlipidemia)
2. Suffering from muscular or neurological diseases not related to FMF
3. With elevated serum creatinine / liver enzymes/ creatine phosphokinase (CPK) levels.
4. Suffering from claustrophobia, or with metal fragments in body tissue, or with other contraindications for MRI.

Patients with FMF, fulfilling the Tel Hashomer criteria for the diagnosis of FMF, suffering from episodes of exertional leg pain and or exertional ankle edema, 18-45 years old, on a stable (≥ 2 weeks) dose of oral colchicine therapy, Non-smokers