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What causes juvenile dermatomyositis?
Last reviewed: 04.07.2025
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The causes of juvenile dermatomyositis are unknown. According to modern concepts, juvenile dermatomyositis is a multifactorial disease that develops as a result of antigen stimulation of an autoimmune response by the type of molecular mimicry under the influence of environmental factors, most likely in genetically predisposed individuals.
Currently, the greatest importance as an etiologic factor is given to infectious agents. Epidemiological studies often indicate infectious diseases during the 3 months preceding the debut of juvenile dermatomyositis. It is assumed that the autoimmune response develops by the mechanism of molecular mimicry due to the similarity of infectious antigens and autoantigens of the macroorganism. Etiologically significant infectious agents in juvenile dermatomyositis: influenza viruses, parainfluenza, hepatitis B, picornaviruses (Coxsackie B), parvovirus, protozoa (Toxoplasma gondii). Among bacterial pathogens, the role of Borrelia burgdorferi and beta-hemolytic streptococcus group A is emphasized.
Other suspected etiologic factors in juvenile dermatomyositis include certain vaccines (typhoid, cholera, hepatitis B, measles, rubella, and mumps), sun exposure, and medications (D-penicillamine, growth hormone).
Cases of familial dermatomyositis support a hereditary predisposition. Important evidence of a hereditary predisposition to the disease is the high (compared to the population) frequency of occurrence of certain immunogenetic markers, in particular leukocyte antigens of the human major histocompatibility complex - HLA BS and DR3.
Pathogenesis of juvenile dermatomyositis
It has now been proven that the key link in the pathogenesis of dermatomyositis in both children and adults is microangiopathy involving endomysial capillaries. The basis of the vascular wall lesion is the deposition of deposits consisting of antibodies to an unknown antigen in endothelial cells and activated components of the complement system C5b-9 in the form of the so-called membrane attack complex (MAC). The deposition of these complexes induces endothelial necrosis, leading to the loss of capillaries, ischemia and destruction of muscle fibers. MAC deposition was detected at the earliest stages of the disease, before changes in the muscles. This process is regulated by cytokines produced by immunocompetent and endothelial cells, which in turn cause the activation of T-lymphocytes, macrophages and secondary destruction of myofibrils.