Recurrent juvenile dermatomyositis and cutaneous necrotizing arteritis with molecular mimicry between streptococcal type 5 M protein and human skeletal myosin.

An adult patient had a syndrome associating the features of juvenile dermatomyositis and cutaneous polyarteritis nodosa that followed a cyclic course from childhood; recurrences were always associated with a rise of serum antistreptococcal antibodies. Regions of homology between streptococcal type 5 M protein and skeletal myosin were found. These findings suggest that streptococcal infection, possibly through a molecular mimicry mechanism, played a role in the pathogenesis of the disease in our patient.