Down syndrome and arterial ischemic stroke in childhood: a potential immunologic link with selective IgG4 subclass deficiency.

We report four children with Down Syndrome (DS) without evidence of congenital heart disease who sustained cerebral infarction in the context of an infectious disease. In one child, stroke occurred in the context of acute infection with Mycoplasma pneumonia. In another child, stroke occurred in the context of Streptococcus oralis (viridans subgroup) infection. In two other children, stroke occurred in the context of a bibasilar pneumonia for which an etiologic agent was not found. All patients had evidence of selective IgG4 subclass deficiency. We followed 8 other children with down syndrome with infectious diseases, but without stroke and a control group of healthy children, and measured the value of IgG4 for each group. We found a statistical significant difference of levels of IgG4 subclass deficiency in the group of stroke, in comparison with the other two groups (P values <0.001). We, therefore, suggest an association between IgG4 subclass deficiency and stroke in DS patients. IgG4 subclass deficiency could conceivably play a role in the high frequency of para-infectious related stroke in this population.