In familial Mediterranean fever, the following protein undergoes mutation-

The gene for familial Mediterranean fever has been cloned, and its product is called pyrin (for its relation to fever). Although its exact function is not known, it has been suggested that pyrin is responsible for regulating acute inflammation, presumably by inhibiting the function of neutrophils. Ref: Pathologic Basis Of Disease 7th ed - Robbins, Coltran (Elsevier, 2005) pg no:85