Estimates of the incidence of FMF in specific eastern Mediterranean populations range from one in 2,000 Arabs to one in 250 Sephardic Jews, one in 500 Armenians, and one in 1,000 Turks.
In both there are ritual differences according to the Sephardic (Spanish), Ashkenazic (German-Polish), Roman (Greek and South Italian) and some minor uses, in the later additions to the Liturgy.
Qaro, a Sephardic (Spanish) Jew, in his Code neglected Ashkenazic (German) customs. These deficiencies Isserles supplied, and the notes of Rema are now included in all editions of Qaro's Code.