Systemic autoimmune connective-tissue and rheumatic diseases: which are they?

• Systemic Lupus Erythematosus: SLE
  
  It is a chronic autoimmune disease of unknown etiology, mainly affecting young women. Its incidence is about 30 cases/million/year. It is a disease that can involve all organs and systems as a result of a systemic accumulation of immune complexes and complement.
  SLE can also be induced by the use of medications.
  In SLE, numerous antibodies are formed against: double and single-helix DNA, Sm, Histones, phospholipids, U1RNP, SSA, SSB, ribosomes, centromere and, additionally, there are rheumatoid factors.
• Mixed connectivitis – Sharp’s syndrome
  
  Sharp described a syndrome characterized by SLE, Scleroderma, Polymyositis associated with high titers of anti-U1 RNP antibodies. This disease mainly affects women between 30 and 50 years of age.
  It should be distinguished from the overlap syndromes, a term used for patients in whom two or more diseases coexist, such as SLE, scleroderma, rheumatoid arthritis, and dermatomyositis.
  Autoantibodies: various types of ANA are present in this disease. However, the presence of high-titer anti-U1RNP antibodies is pathognomonic.
• Sjögren’s syndrome
  
  It is a chronic autoimmune disease mostly affecting women aged around 50, the prevalence of which is unknown. There is a primary, or isolated, form and a secondary form associated with other connective tissue diseases such as SLE.
  30% of SS cases may be associated with rheumatoid arthritis, 10% to SLE and 1% to scleroderma.
  Furthermore, this disease is associated with polyarteritis nodosa or polymyositis. SS can also be associated tp Hashimoto’s thyroiditis (in 50% of the cases, anti-thyroid autoantibodies are present with or without signs of gland dysfunction) or to other organ-specific autoimmune diseases, such as diabetes mellitus, vitiligo, and primitive biliary cirrhosis.
  Autoantibodies:
  In SS, ANA can be found in about 70% of the cases and rheumatoid factors in about 80% of the cases.
  Anti-SSA and anti-SSB antibodies can also be identified. They are generally present simultaneously in both the primary and the secondary form, associated with SLE.
• Sclerodermia
  
  It is a chronic autoimmune disease of unknown etiology with an incidence of about 18 cases/million/year. Adult age and female gender influence the development of the disease which usually appears between 30 and 60 years of age.
  The disease includes various clinical forms:
  Localized scleroderma and Generalized or progressive systemic scleroderma, of which three forms exist:
  1) diffuse scleroderma with a slow and progressive course, which is occasionally acute and fatal, with a rapid systemic involvement;
  2) CREST syndrome (acronym for calcinosis, Raynaud’s, esophageal involvement, sclerodactyly and telangiectasia):
  3) secondary scleroderma-like syndromes. Raynaud’s phenomenon is an important clinical sign associated with scleroderma and, occasionally, it can even precede it. Indeed, 5-10% of the cases developing Raynaud’s phenomenon progress towards a connective tissue disease, mainly of the scleroderma group.
  Positivity to the rheumatoid factor in 25% of the cases.
  Major Autoantibodies: various types of circulating antinuclear antibodies can be present, most notably: anti-Scl-70, anti-centromere, anti-PM-Scl, ss-DNA , RNP
• Cryptogenic fibrosing alveolitis
  
  It is an idiopathic lung disease, at times associated with connective tissue diseases (particularly scleroderma and SLE), which can present antinuclear antibodies and circulating immune complexes.
• Rheumatoid arthritis
  
  The criteria classification for RA include the rheumatoid factor (RF) serum markers. An association between the presence of RF and increasing joint damage followed by disability has been demonstrated, especially if there is a high-titer RF presence.
  Nevertheless, RF is often negative or present in low-titers at the early stages of the disease. It has been demonstrated that anti-cyclic citrullinated peptide (CCP) and anti-mutated citrullinated Vimentin antibodies can be detected in a significant number of patients with RA with an excellent specificity towards negative sera.
  Anti CCP antibodies can be detected years before the onset of clinical manifestations and can, therefore, be used as a predictive marker for RA development.
• Autoantibodies in connective tissue and rheumatic diseases (% values)

MC= mixed connectivitis; PSS= Progressive Systemic Scleroderma;
DM/PM=Dermatomyositis/ Polymyositis; SS= Sjögren’s Syndrome