Neonatal lupus manifests as isolated neutropenia and mildly abnormal liver functions.
Neonatal lupus is characterized by typical clinical features and the presence of maternal autoantibodies. Mothers can have systemic lupus erythematosus (SLE) or Sjögren's syndrome, but are commonly not affected with any clinical disease. The major clinical manifestations in the infants are cardiac, dermatological and hepatic with rare instances of hemolytic anemia, thrombocytopenia or neutropenia. We describe an infant born to a mother with anti-Ro and anti-La, who had neutropenia and mildly abnormal liver functions without other major clinical features of neonatal lupus such as cardiac or dermatological manifestations. Neutropenia improved as maternal antibody was metabolized. Antibodies from both the infant and mother bound intact neutrophils, and this binding was inhibited by 60 kDa Ro. These data imply neutropenia may be an isolated manifestation of neonatal lupus. We studied the anti-Ro antibodies of 2 other mothers who gave birth to infants with complete congenital heart block and neutropenia. Their sera also bound neutrophils. Because healthy infants do not commonly undergo complete blood counts, the incidence of neutropenia among infants of anti-Ro-positive mothers may be much higher than previously recognized. Furthermore, although other factors may contribute, these data suggest that anti-60 kDa Ro is directly involved in the pathogenesis of neutropenia.