Macrophage activation syndrome in neonates born to mothers with adult-onset Still's disease: Perinatal effect of maternal IL-18.

Overproduction of interleukin (IL)-18 is closely related to the pathogenesis of adult-onset Still's disease (AOSD) and the development of macrophage activation syndrome (MAS), a life-threating complication of AOSD. We reported three cases of MAS occurring in infants born to mothers with AOSD. The infants developed MAS at age 13 and 8 days and at birth. Serum IL-18 levels were extremely elevated in all infants (147,000 pg/mL; 378,000 pg/mL; 95,000 pg/mL) as well as in their mothers (58,500 pg/mL; 367,000 pg/mL; 84,000 pg/mL). Physicians should be aware that infants born to mothers with AOSD are at a risk of developing MAS. Serum IL-18 levels in mothers with AOSD and their infants should be monitored.