Juvenile idiopathic inflammatory myositis: an update on pathophysiology and clinical care

Abstract

The childhood-onset or juvenile idiopathic inflammatory myopathies (JIIMs) are a heterogenous group of rare and serious autoimmune diseases of children and young people that predominantly affect the muscles and skin but can also involve other organs, including the lungs, gut, joints, heart and central nervous system. Different myositis-specific autoantibodies have been identified that are associated with different muscle biopsy features, as well as with different clinical characteristics, prognoses and treatment responses. Thus, myositis-specific autoantibodies can be used to subset JIIMs into sub-phenotypes; some of these sub-phenotypes parallel disease seen in adults, whereas others are distinct from adult-onset idiopathic inflammatory myopathies. Although treatments and management have much improved over the past decade, evidence is still lacking for many of the current treatments and few validated prognostic biomarkers are available with which to predict response to treatment, comorbidities (such as calcinosis) or outcome. Emerging data on the pathogenesis of the JIIMs are leading to proposals for new trials and tools for monitoring disease.

Juvenile Dermatomyositis: Association between Nail Fold Capillary End Row Loops Area Under the Curve and Disease Damage Indicators

“…Circulating endothelial cells and markers of endothelial injury, such as vWF:Ag, and thrombomodulin, aree elevated in JDM, providing further evidence of endothelial involvement in the disease pathophysiology ( 8 , 16 , 17 ). B cell activation and expansion as well as the formation of anti-endothelial cell antibodies have been demonstrated in JDM ( 18 – 21 ), suggesting another potential mechanism for endothelial cell injury.…”

“…Despite medical therapy, the mean ERL count in JDM patients remained below normal even after five years of treatment, particularly in the polyphasic and chronic disease courses. This implies that the restoration of capillary density might be challenging to achieve and may require novel therapeutic strategies to target endothelial dysfunction effectively ( 16 ).…”

Anti-synthetase syndrome in a child with pneumomediastinum: a case report and literature review

“…Previous studies revealed the similar phenotype of ASS in juveniles and adults, although this subtype is much less frequent in childhood than in adulthood. Important features such as Raynaud phenomenon, mechanics hands and ILD seem to occur at a lower frequency in childhood-onset disease than in adult-onset disease [ 8 ].…”

Juvenile dermatomyositis: association between nail fold capillary end row loop– area under the curve– and disease damage indicators

“…Despite medical therapy, the mean ERL count in JDM patients remained below normal levels even after five years of treatment, particularly in the polyphasic and chronic disease courses. This implies that the restoration of capillary density might be challenging to achieve and may require additional novel therapeutic strategies to target endothelial dysfunction effectively [ 19 ].…”

“…Circulating endothelial cells and markers of endothelial injury, such as vWF antigen, and thrombomodulin are elevated in JDM, providing further evidence of endothelial involvement in the disease pathophysiology [ 8 , 19 , 20 ]. B cell activation and expansion as well as the formation of anti-endothelial cell antibodies have been demonstrated in JDM [ 21 – 24 ], suggesting other potential mechanisms for endothelial cell injury.…”