Clinical and subclinical inflammation in patients with familial Mediterranean fever and in heterozygous carriers of MEFV mutations

Autoinflammatory diseases

Autoinflammatory diseases can be specified as inborn errors of the innate immune system. The main component of autoinflammatory diseases is the group of hereditary periodic fevers which are characterised by intermittent bouts of clinical inflammation with focal organ involvement mainly: abdomen, musculoskeletal system and skin. The most frequent one is familial Mediterranean fever that affects patients of Mediterranean descent all over the world. Recently, three other types have been characterised, clinically as well as genetically: Tumor Necrosis Factor receptor superfamilly 1A Associated Periodic Fever Syndrome, hyperimmunoglobulinemia D and periodic fever syndrome/ mevalonate kinase deficiency, and the most recently recognised entity which includes Muckle Wells, familial cold autoinflammatory/familial cold urticaria, and the Chronic infantile neurological cutaneous and articular/Neonatal onset multisystemic inflammatory disease syndromes. A thorough diagnosis is warranted, as clinical and therapeutic management is specific for each of these diseases. In addition to hereditary periodic fever, autoinflammatory diseases also encompass Blau, Majeed, and PAPA syndromes. The underlying genetic defects of these inflammatory diseases appear to be specific for each type, involving several so far unknown proteins involved in innate immunity, and have already opened new avenues in our understanding of the inflammatory response.

Hereditary auto-inflammatory disorders and biologics

The term auto-inflammatory disorders has been coined to describe a group of conditions characterized by spontaneously relapsing and remitting bouts of systemic inflammation without apparent involvement of antigen-specific T cells or significant production of auto-antibodies. The hereditary periodic fever syndromes are considered as the prototypic auto-inflammatory diseases, and genetic studies have yielded important new insights into innate immunity. DNA analysis has greatly enhanced the clinical characterization of these conditions, and elucidation of their molecular aetiopathogenesis has suggested that therapies may be aimed at specific targets within the immune cascade. The availability of biologic response modifiers such as inhibitors of tumour necrosis factor (TNF) and interleukin-1beta has greatly improved the outlook for some of these disorders, although effective therapies remain elusive in patients with certain conditions, including hyperimmunoglobulinaemia-D with periodic fever syndrome (HIDS) and a proportion of those with TNF-receptor associated periodic syndrome (TRAPS). Indeed, outstanding challenges and the unique potential to further elucidate molecular mechanisms in innate immunity are illustrated by the dashed early hope that TNF blockade would be a panacea for TRAPS: not only is etanercept (Enbrel) ineffective in some cases, but there are anecdotal reports of this condition being greatly exacerbated by infliximab (Remicade).