Research explains immune system malfunction behind familial Mediterranean fever attacks
Two August 2026 studies in Science Immunology reveal the molecular mechanism behind familial Mediterranean fever. Researchers identified the protein CDC42 as the direct binding partner of pyrin. Mutations in either the CDC42 gene (such as T43I) or the MEFV gene (such as M694V) abnormally strengthen this interaction, causing pyrin to clump and trigger severe inflammatory attacks. A new functional atlas of 265 MEFV variants enables precise diagnoses and subtype-specific treatments.
Pyrin-CDC42 interaction mechanism
▪Two August 2026 studies published in Science Immunology established that the protein CDC42 is the direct binding partner that triggers pyrin-driven familial Mediterranean fever attacks.
▪Under normal conditions, the innate immune sensor pyrin briefly interacts with the small cellular GTPase CDC42 to trigger a controlled inflammatory response.
▪Pathologically enhanced interactions between pyrin and CDC42 cause pyrin to assemble into abnormal clumps, releasing inflammatory signals and triggering cell rupture.
CDC42 T43I mutation
▪Researchers identified a previously unreported T43I mutation in the CDC42 gene in six patients from three unrelated families presenting with severe inflammatory symptoms.
▪The CDC42 T43I mutation reshapes a surface hairpin loop on CDC42, causing it to bind abnormally tightly to the tail end of the pyrin protein.
MEFV variant functional atlas
▪Researchers introduced 265 MEFV gene variants into human cells to construct a functional atlas classifying the variants as gain-of-function, loss-of-function, or neutral.
▪The MEFV functional atlas provides clinical utility by converting hundreds of previously uninterpretable genetic variants of uncertain significance into clear diagnostic answers.
FMF B30.2 domain mutations
▪Classical familial Mediterranean fever mutations, including M680I, M694V, and M694I, cluster on a single patch of the pyrin B30.2 domain that contacts CDC42.
▪Experiments showed that removing CDC42 from cells halts the hyperactive pyrin clump formation and inflammation driven by classical familial Mediterranean fever mutations.
Precision medicine approaches
▪Identifying CDC42 as a direct regulator of pyrin provides a novel therapeutic target to prevent runaway inflammatory activation in severe autoinflammatory diseases.
▪Because some MEFV mutations activate pyrin independently of CDC42, future treatments can be tailored to a patient's specific molecular subtype.
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