Incomplete KD
This is another exception, which seems to be a more frequent diagnosis in the past decade. Incomplete KD requires the 5 days of fever duration plus an elevated C-reactive protein or erythrocyte sedimentation rate. But one needs only two or three of the five principal clinical KD criteria plus three or more of six other laboratory findings (anemia, low albumin, leukocytosis, thrombocytosis, pyuria, or elevated alanine aminotransferase). Incomplete KD can be confirmed by an abnormal echocardiogram – usually not until after 7 days of KD symptoms.1
New KD nuances
In a recent report on 20 years of data from Japan (n = 1,945 KD cases), more granularity on age, seasonal epidemiology, and outcome were seen.2 There was an inverse correlation of male predominance to age, i.e. as age groups got older, there was a gradual shift to female predominance by 7 years of age. The winter/spring predominance (60% of overall cases) did not hold true in younger age groups where summer/fall was the peak season (65% of cases).
Dr. Christopher J. Harrison
Finally, despite treatment, coronary artery abnormalities were observed the least frequently in 11- to 47-month-olds (1.9%) and most frequently in those younger than 4 month olds (5.8%) and older than 83 month olds (6.6%). Keep in mind that Japan has a higher rate of coronary artery abnormalities than that of the United States. Also, the relative infrequency of KD in the oldest and youngest age groups may have led to later diagnosis in these two age groups, leading to less benefit from intravenous immunoglobulin treatment.
With the goal of not missing any KD and diagnosing as early as possible to limit sequelae, we all need to be relative experts and keep alert for clinical scenarios that warrant our raising our index of suspicion. But now the seasonality trends appear blurred in the youngest cases and the male predominance is blurred in the oldest cases. And remember that fever and irritability for longer than 7 days in young infants may be the only clue to KD.
Dr. Harrison is professor of pediatrics and pediatric infectious diseases at Children’s Mercy Hospitals and Clinics, Kansas City, Mo. He said he had no relevant financial disclosures. Email him at [email protected].
References
1. Circulation. 2017 Mar 29. doi: 10.1161/CIR.0000000000000484
2. N Engl J Med. 2018 May 24. doi: 10.1056/NEJMc1804312.
