Protracted febrile myalgia (PFM) is a rare form of vasculitic disease that affects patients with familial Mediterranean fever (FMF). Mutation analysis performed in 15 patients who suffered from this disorder showed that 9 of the 15 patients were homozygous for M694V. FMF in these 9 patients was associated with more severe symptoms compared to a group of 30 M694V homozygous FMF patients without PFM.