Why the body's inflammatory alarm misfires in familial Mediterranean fever

Familial Mediterranean fever (FMF) is an inherited autoinflammatory condition triggered by the body's immune system overreacting to minor or irrelevant triggers, resulting in frequent fever episodes and inflammatory pain. The root cause lies within the MEFV gene, which produces a protein called pyrin that forms part of a protein assembly called an inflammasome - a natural alarm system detecting threats like bacteria and launching inflammation to defend the body.

Under normal circumstances, pyrin is regulated by an internal 'brake' activated by bacterial toxins, specific drugs, or mutations in pyrin or its regulators. When this brake is disengaged, pyrin forms large clumps releasing inflammatory signals, causing the painful flare-ups common in FMF.

For decades, researchers have puzzled over how the 'brake' is released in FMF. Recent studies shed light on this mechanism. Both found that pyrin interacts with a protein called CDC42. The first study identified a previously unknown mutation in CDC42 linked to severe FMF symptoms. This mutation caused CDC42 to excessively cling to pyrin, causing the inflammatory system to activate abnormally and lead to cell rupture.

The second study applied a 'genotype-first' approach, introducing various MEFV mutations into human cells and analyzing their effects. They discovered that some mutations, previously considered insignificant, drove disease by making pyrin grip CDC42 too tightly, accelerating clump formation and inflammation. Other mutations activated pyrin independently of CDC42, suggesting multiple pathways to pyrin activation.

Together, these studies clarify how FMF occurs - through improper pyrin-CDC42 interaction leading to excessive inflammation. This insight also offers a path to more accurate diagnoses and targeted treatments for FMF and related conditions.