Diagnosis of FMF relies on clinical assessments, with additional genetic testing. Different sets of criteria have been developed, but they are yet to be validated in all populations affected by FMF. The most widely used criteria are the 1997 Tel Hashomer criteria, however these do not incorporate genetic testing.[59] In children, the Yalcinkaya-Ozen criteria have been shown to be more sensitive for diagnosis of FMF in children, compared with the Tel Hashomer criteria.[60][61] In 2019, genotype and clinical manifestations were combined to form a classification criteria for hereditary recurrent fevers.[5] Although these are useful for the accurate identification of diseases for studies, they are not designed for diagnostic purposes.

In the typical form of FMF, the diagnosis is often obvious. At the beginning of the disease, when clinical signs are atypical or when the familial history is lacking, genetic testing is of great value. In a clinical context of FMF, the presence of 2 mutations on different alleles (homozygosity or compound heterozygosity) confirms the diagnosis.[53] When only 1 mutation is present, the diagnosis is unconfirmed; nevertheless, diagnosis should not be ruled out if the clinical presentation is typical, because some rare or unknown mutations do exist. The registry of hereditary auto-inflammatory disorders mutations external link opens in a new window

Those same 'true' heterozygotes may display a complete clinical picture of FMF. It is also likely that some heterozygous patients, as in many recessive diseases, may have attenuated clinical signs. Even though the genetic diagnosis provides no final solution for every patient, it has become an important diagnostic tool for the confirmation of FMF diagnosis and, consequently, the provision of appropriate treatment, especially in children.[58]

FMF’s major complication is systemic secondary amyloidosis. This can readily be prevented by colchicine prophylaxis, which explains the need for prompt and accurate diagnosis.

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