Autoimmunity - Classification

Classification

Autoimmune diseases can be broadly divided into systemic and organ-specific or localised autoimmune disorders, depending on the principal clinico-pathologic features of each disease.

• Systemic autoimmune diseases include SLE, Sjögren's syndrome, scleroderma, rheumatoid arthritis, and dermatomyositis. These conditions tend to be associated with autoantibodies to antigens which are not tissue specific. Thus although polymyositis is more or less tissue specific in presentation, it may be included in this group because the autoantigens are often ubiquitous t-RNA synthetases.

• Local syndromes which affect a specific organ or tissue:
  • Endocrinologic: Diabetes mellitus type 1, Hashimoto's thyroiditis, Addison's disease
  • Gastrointestinal: Coeliac disease, Crohn's Disease, Pernicious anaemia
  • Dermatologic: Pemphigus vulgaris, Vitiligo
  • Haematologic: Autoimmune haemolytic anaemia, Idiopathic thrombocytopenic purpura
  • Neurological: Myasthenia gravis

Using the traditional “organ specific” and “non-organ specific” classification scheme, many diseases have been lumped together under the autoimmune disease umbrella. However, many chronic inflammatory human disorders lack the telltale associations of B and T cell driven immunopathology. In the last decade it has been firmly established that tissue "inflammation against self" does not necessarily rely on abnormal T and B cell responses.

This has led to the recent proposal that the spectrum of autoimmunity should be viewed along an “immunological disease continuum,” with classical autoimmune diseases at one extreme and diseases driven by the innate immune system at the other extreme. Within this scheme, the full spectrum of autoimmunity can be included. Many common human autoimmune diseases can be seen to have a substantial innate immune mediated immunopathology using this new scheme. This new classification scheme has implications for understanding disease mechanisms and for therapy development (see PLoS Medicine article. http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0030297).