Overt and occult rheumatic diseases: the child with chronic fever.

Identification of the genes involved in hereditary periodic fever syndromes has led to the recognition of a new pathophysiological category, the autoinflammatory disorders. The main non-hereditary autoinflammatory disease in childhood is systemic juvenile idiopathic arthritis (sJIA), others being the chronic infantile neurological cutaneous arthropathy (CINCA) syndrome and the periodic fever, aphthous stomatitis, pharyngitis and adenopathy (PFAPA) syndrome. Familial Mediterranean fever (FMF) has been traced to mutations in the MEFV gene. Mutations in the MVK gene, encoding the enzyme mevalonate kinase, cause the hyper-IgD periodic fever syndrome (HIDS). The tumour necrosis factor(TNF)-receptor-associated periodic syndromes (TRAPS) have been linked to mutations in theTNFRSF1A gene, encoding a TNF-alpha receptor, and the CIAS1 gene is mutated in familial cold autoinflammatory syndrome. We discuss how this knowledge has influenced diagnosis and treatment of these rare genetic disorders and how it might change our approach to the more common rheumatic diseases.