Familial Mediterranean fever

Familial Mediterranean fever is primarily a genetic disease due to Mendelian-recessive inheritance of Mediterranean fever gene mutations.

Occurs mainly in people of Mediterranean ancestry, especially from Arab countries, Turkey, Israel, and Armenia.

Characterised by recurrent attacks of fever and systemic inflammation, typically lasting 24-72 hours and presenting in childhood.

Rare manifestations include chronic arthritis, spondyloarthropathy, myopathies, and protracted febrile myalgia.

Clinical judgement is important in establishing the diagnosis, which is often made retrospectively.

Majority respond to colchicine, which is almost always diagnostic and distinguishes from other inherited periodic fever syndromes.

Colchicine is the only proven treatment and prevents the most serious and life-threatening complication, renal amyloidosis.

Familial Mediterranean fever (FMF; phenotype Mendelian Inheritance in Man number 249100) is part of the currently expanding family of auto-inflammatory disorders.The disease originated over 2000 years ago in western Asia and spread to the Mediterranean basin and the rest of the globe with the advent of extensive global migration. First classified as a clinical disease by Siegal in 1949, this genetic disorder of specific populations has both clinical and genetic definitions.[1]Siegal S. Benign paroxysmal peritonitis. Gastroenterology. 1949 Feb;12(2):234-47. http://www.ncbi.nlm.nih.gov/pubmed/18124924?tool=bestpractice.com [2]Grateau G. Clinical and genetic aspects of the hereditary periodic fever syndromes. Rheumatology (Oxford). 2004 Apr;43(4):410-5. http://rheumatology.oxfordjournals.org/content/43/4/410.long http://www.ncbi.nlm.nih.gov/pubmed/14983109?tool=bestpractice.com

The clinical definition is recurrent self-limiting attacks of fever, severe abdominal pain, arthralgias or monoarthritis, pleurisy, or an erysipeloid rash on one ankle or foot, typically lasting 24-72 hours. FMF mainly affects populations from the Mediterranean basin, especially people of Arab, Turkish, Sephardic Jewish, and Armenian ancestry, in whom the disease is relatively frequent. For the majority of patients, the first clinical signs appear during childhood.

The genetic definition is disease caused by Mendelian-recessive inheritance due to mutations in the Mediterranean fever (MEFV) gene coding for a protein named marenostrin/pyrin. MEFV gene analysis is the only objective tool that confirms the diagnosis of FMF. However, MEFV carriers sometimes present with FMF-like disease. Mutation analysis in a large series showed that up to 30% of clinical FMF patients had a single mutated allele only in the MEFV gene.[3]Zaks N, Shinar Y, Padeh S, et al. Analysis of the three most common MEFV mutations in 412 patients with familial Mediterranean fever. Isr Med Assoc J. 2003 Aug;5(8):585-8. http://www.ima.org.il/FilesUpload/IMAJ/0/54/27241.pdf http://www.ncbi.nlm.nih.gov/pubmed/12929299?tool=bestpractice.com [4]Tunca M, Akar S, Onen F, et al; Turkish FMF Study Group. Familial Mediterranean fever (FMF) in Turkey: results of a nationwide multicenter study. Medicine (Baltimore). 2005 Jan;84(1):1-11. http://www.ncbi.nlm.nih.gov/pubmed/15643295?tool=bestpractice.com The reason FMF carriers may express symptoms is still unclear. Therefore, the diagnosis remains predominantly clinical because mutations cannot always be identified on both alleles, even after complete gene analysis.

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.