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Specific perinatal exposures may increase risk for Kawasaki disease
Bacterial infection, maternal age and birth origin of the mother all may play a role in Kawasaki disease, according to recent study findings.
Kristen Hayward, MD, MS, and colleagues from the University of Washington School of Medicine and Seattle Children’s Hospital examined discharge records to identify 995 children who were hospitalized with Kawasaki disease (KD) in Washington state between 1987 and 2007. These records were linked to birth certificates and birth hospitalization discharge records for the purpose of the study, in which researchers obtained maternal and infant exposure information.
Researchers found a weak, positive link between a maternal age of at least 35 years and mothers of foreign birth with KD. Maternal colonization with group B streptococcus was associated with a reduced risk for KD. The researchers noted no association between KD and other maternal infections, vascular factors or maternal autoimmune disease. Hayward and colleagues said children hospitalized in the first 6 months of life were 1.42 times more likely to develop KD and were three times more likely to be diagnosed than nonhospitalized infants if the reason for hospitalization was bacterial infection.
The researchers also said infants of Asian and black race were more likely to be diagnosed with KD than other races, which has been reported previously.
“These findings potentially support the hypothesis that exposure to certain infections during a critical period in infancy may prime the developing immune system in ways that predispose to later KD,” they said. “Alternatively, this association could indicate that infants with an increased susceptibility to infections might harbor a subtle immune deficit which also renders these children prone to KD. Lastly, it is possible that other factors associated with hospitalization for infections, such as receipt of antibiotics, rather than the infection itself, might be responsible for the observed associations.”
Disclosure: Dr. Hayward reports no relevant financial disclosures.
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Using administrative data (not clinical), Hayward and colleagues assessed whether certain perinatal exposures correlated with the later development of Kawasaki disease (KD) in a retrospective case-control study. They observed that, compared with race, gender, and birth year-matched controls, KD was associated with older maternal age, foreign-born mother, lower rate of maternal group B streptococcus (GBS) colonization and higher rates of hospitalizations in the first 6 months of life, especially for apparent bacterial illness. Some of the findings can be explained by the well-known tendency for KD to skew toward somewhat higher socioeconomic status subjects compared with non-KD controls. These findings include older maternal age and lower perinatal GBS carriage rates, for example.
It is not at all clear why KD patients would have an increased likelihood of being hospitalized in the first 6 months of life for a bacterial illness, compared with non-KD controls. This conclusion is based solely on administrative data, that is, data derived from ICD-9 codes rather than upon review of actual clinical information. In my experience, coding errors are quite common, and the investigators considered coded diagnoses for hospitalization for children aged younger than 6 months as bacterial to include the following ICD-9 codes: 486, pneumonia, unspecified; 770.0, congenital pneumonia; 771.8, other infections specific to the perinatal period; and 777.5, necrotizing enterocolitis, among others. The accuracy of these coding data and assumptions is somewhat questionable. Additional studies that utilize clinical chart reviews will be needed to confirm the conclusions of this study that early infancy exposures (especially hospitalization for bacterial infection) somehow predispose to later KD.
The bulk of scientific evidence at present supports the hypothesis that a specific ubiquitous infectious agent, such as a virus, causes KD when it infects a genetically susceptible host, but the final chapter in this story has not yet been written.