Exertional leg pain in familial mediterranean Fever: a manifestation of an underlying enthesopathy and a marker of more severe disease.

[familial mediterranean fever]

Exertional leg pain is a characteristic musculoskeletal manifestation of familial Mediterranean fever (FMF ). We aimed to define the frequency and characteristics of exertional leg pain in a large cohort of FMF patients and to evaluate for additional signs and symptoms of spondyloarthritis (SpA ) in this patient population .FMF patients were allocated into study or control groups based on the presence or absence of exertional leg pain . Randomly selected patients underwent magnetic resonance imaging (MRI ) of the ankle as well as plain radiography of the sacroiliac joints .The prevalence of exertional leg pain among the 170 FMF patients included in the study was 58 .2 %. Patients with exertional leg pain had significantly more joint attacks (74 .7 % versus 40 .8 %; P < 0 .0001 ), fever attacks (35 .4 % versus 15 .5 %; P = 0 .004 ), and pleuritis attacks (48 .5 % versus 29 .6 %; P = 0 .013 ) as well as more attacks per year . Elevations of inflammation markers were significantly more frequent among the study group (for the erythrocyte sedimentation rate , 44 .4 % of patients versus 21 .1 % of patients ; P = 0 .016 ) (for the C-reactive protein level , 48 .4 % of patients versus 31 .8 % of patients ; P = 0 .013 ), and M 694 V homozygosity was more prevalent among the study group (45 .5 % versus 21 .1 %; P = 0 .001 ). Signs compatible with enthesopathy on MRI were observed in 73 .5 % of patients in the study group and in 33 .3 % of patients in the control group (P = 0 .046 ). Definite SpA was diagnosed in 41 .2 % of the patients in the study group compared to none of the controls (P = 0 .07 ) (odds ratio 1 .7 [95 % confidence interval 1 .2 -2 .3 ]).Exertional leg pain is a common manifestation of FMF and is a marker of a more severe disease phenotype . Additionally , exertional leg pain is frequently associated with sacroiliitis and an underlying ankle enthesopathy and should therefore be considered a new feature of SpA .