Molecular characteristics and functional differences of anti-PM/Scl autoantibodies and two other distinct and unique supramolecular structures known as "EXOSOMES"

Probable role of exosomes in the extension of fibrotic alterations from affected to normal cells in systemic sclerosis

SSc is a systemic autoimmune disease of unknown etiology characterized by frequently progressive cutaneous and internal organ fibrosis causing severe disability, organ failure and high mortality. A remarkable feature of SSc is the extension of the fibrotic alterations to nonaffected tissues. The mechanisms involved in the extension of fibrosis have remained elusive. We propose that this process is mediated by exosome microvesicles released from SSc-affected cells that induce an activated profibrotic phenotype in normal or nonaffected cells. Exosomes are secreted microvesicles involved in an intercellular communication system. Exosomes can transfer their macromolecular content to distant target cells and induce paracrine effects in the recipient cells, changing their molecular pathways and gene expression. Confirmation of this hypothesis may identify the molecular mechanisms responsible for extension of the SSc fibrotic process from affected cells to nonaffected cells and may allow the development of novel therapeutic approaches for the disease.

Anti-polymyositis/Scl antibody-positive overlap syndrome of diffuse cutaneous systemic sclerosis, dermatomyositis, systemic lupus erythematosus, and antiphospholipid syndrome

A 37-year-old Japanese man with a 3-year history of diffuse cutaneous systemic sclerosis was admitted to our hospital with high fever, arthralgia, myalgia, and muscle weakness. A physical examination revealed facial erythema, Gottron's sign, and mechanic's hands in addition to skin sclerosis. Laboratory data revealed significantly elevated levels of creatine kinase and decreased complement. Anti-RNP, anti-Smith, anti-DNA, anti-β₂ -glycoprotein 1, anti-polymyositis (PM)/Scl75, and anti-PM/Scl100 antibodies were detected. He also had urinary protein, interstitial lung disease, pericarditis, multifocal cerebral infarctions, and leukoencephalopathy. Thus, a diagnosis of overlap syndrome of diffuse cutaneous systemic sclerosis, dermatomyositis, and systemic lupus erythematosus with antiphospholipid syndrome was made. Because of the intractable course, he was treated with multiple immunosuppressive and immunomodulatory drugs, including three rounds of 1000 mg methylprednisolone pulse therapy. This is the first case report of anti-PM/Scl antibody-positive overlap syndrome of three major connective tissue diseases.