Staphylococcal infections in childhood dermatomyositis--association with the development of calcinosis, raised IgE concentrations and granulocyte chemotactic defect.

There is a high incidence of staphylococcal infection in children with dermatomyositis, which is limited to those children who either already have or subsequently develop calcinosis. Of 15 children followed up for 3-10 years after diagnosis, all nine who developed calcinosis had infections with Staphylococcus aureus compared with none of six without calcinosis. Of these nine, the occurrence of staphylococcal infections before calcinosis was observed in four, suggested by history in two, and unclear in three children. Granulocyte chemotaxis to Staphylococcus aureus was more severely depressed in those children with calcinosis, whereas those without calcinosis did not differ significantly from controls. The chemotactic defect was due to a serum factor (patients' serum depressed control chemotaxis and control serum corrected the patients' chemotaxis). The nine children with calcinosis also had significantly higher serum IgE concentrations than non-atopic age matched controls; the six without calcinosis did not differ from controls. The increased IgE concentrations appeared to develop after staphylococcal infection and before calcinosis. Two of five patients with calcinosis had increased antistaphylococcal IgE antibodies; neither of the two patients without calcinosis had such increased antibodies. This suggests preceding immunological differences in patients with dermatomyositis who do and do not subsequently develop calcinosis, either increasing susceptibility to Staphylococcus aureus infection or potentially resulting from such infections.