Pattern of proteinuria in patients with renal amyloidosis secondary to familial Mediterranean fever

[Familial Mediterranean fever among the autoimmune diseases]

During the first attacks of familial Mediterranean fever, each of the disease symptoms can suggest a series of disorders. When the disease is older, the recurrence of symptoms may simulate some systemic diseases, but mainly suggests familial Mediterranean fever, one of a group of hereditary autoinflammatory diseases. Before the gene for familial Mediterranean fever was identified, various sets of criteria were used for diagnosis. The presence of MEFV mutations confirms the diagnosis, but the clinical criteria still determine who should undergo this genetic testing. The genotype-phenotype correlations add a prognostic dimension to the mutations identified. Genotyping can also lead to the diagnosis of the other autoinflammatory diseases, which constitute the basis of the differential diagnosis of familial Mediterranean fever. The hyperimmunoglobulinemia D syndrome (HIDS) is very similar to familial Mediterranean fever in its recessive transmission and abdominal and articular symptoms. It can be distinguished by the European origin of the patients, the presence of cervical lymph nodes and the increased IgD levels. Of the diseases with dominant transmission, the TNF receptor-associated periodic syndromes (TRAPS) are suggested by periorbital edema and migrating inflammatory cellulitis. Muckle and Wells syndrome is revealed by episodes of fever with urticaria and arthralgia, complicated by deafness and amyloidosis. Mutations in the same gene are responsible for two disorders, both appearing in childhood: familial cold urticaria syndrome (FCUS) and chronic infantile neurocutaneous articular syndrome (CINC). The pathogenesis of familial Mediterranean fever is still unclear. Pyrin/marenostrin, the protein produced by the MEFV gene, appears to hae a physiological antiinflammatory effect that inhibits proinflammatory cytokines. Mutation of the gene may eliminate this feedback mechanism and expose the patient to flares from any inflammatory stimulus, even minimal. Amyloid is produced by the serum amyloid A protein (SAA), and its occurrence is influenced by the type of MEFV mutation, but also the genotype of the gene producing SAA.