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Hereditary periodic fever syndromes are defined by the presence of recurrent incapacitating episodes or fluctuating degrees of fever and inflammation in the absence of infection. Unlike autoimmune diseases, hereditary periodic fever syndromes are marked by the absence of significant levels of autoantibodies and autoreactive T-cells. As a consequence, the name autoinflammatory syndromes has been advocated as a common descriptive denominator for this group of rare disorders.1,2 Since 1997, ten of the major syndromes have been linked to mutations in seven specific genes, facilitating the specific diagnosis of these conditions rather than relegating them to diagnoses of exclusion3 (Table 61–1). The nomenclature of the various autoinflammatory syndromes is complicated, comprising a mix of syndromes described by various typical manifestations and syndromes characterized by identification of specific genetic defects. Most terms originated from the period preceding the discovery of the implicated genetic defects. To confound matters even more, most autoinflammatory syndromes are known by more than one name based on personal and geographical preferences. For the purpose of this chapter we use the most accepted terms as retained in the literature.
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The incidence and prevalence of autoinflammatory syndromes vary by ethnicity and geographic location. For instance, FMF, the most common autoinflammatory syndrome, has a high prevalence among Sephardic Jews (100–400 patients per 100,000 persons) and among residents of Turkey (93 patients per 100,000 inhabitants) but a much lower prevalence among Western Europeans (2.5 patients per 100,000 inhabitants).4,5 The prevalence of the other syndromes, while not specifically known, is estimated to be much lower than FMF. The syndrome of periodic fever, aphthous stomatitis, pharyngitis, and cervical adenopathy (PFAPA) is the most common of the remaining syndromes with more than 400 cases reported in English literature since 1989.6 Pyogenic sterile arthritis, pyoderma gangrenosum, and acne (PAPA) and Majeed syndrome are probably the least common with five and three affected families reported, respectively.7–9 The prevalence of other autoinflammatory syndromes is unclear, but each probably ...