Interleukin 17 (IL-17) is a pro-inflammatory cytokine produced by a distinct subset of helper T cells known as T helper type 17 (Th17) cells. Th17 cells, and IL-17 produced by them, have a profound inflammatory action through upregulation of other cytokines and involvement of matrix metalloproteinases. Th17 cells have been incriminated in a host of autoimmune and allergic disorders. A derangement in relative proportions of Th17 and regulatory T cells (Treg) in patients with Kawasaki disease has been reported during the acute phase [5]. The proportion of Th17 cells was elevated whereas that of Treg was decreased during the acute phase. Th17 cell numbers were significantly higher in patients with Kawasaki disease resistant to IVIg compared to those who responded to immunoglobulin therapy [5].

Natriuretic peptides such as brain natriuretic peptides are synthesized by the ventricular myocytes in response to myocardial stress and injury in a wide variety of disorders such as congestive heart failure, acute coronary syndromes, and following major surgeries. Brain natriuretic peptide (BNP) is synthesized in a precursor form, PreproBNP, from the cardiac myocytes. It is first cleaved in the liver to form ProBNP which is further cleaved by an endopeptidase in the blood to form BNP and N-terminal pro-BNP (NTpro-BNP). NTpro-BNP is an inactive cleavage product which has a longer half-life in circulation than pro-BNP. Some previous studies have evaluated the diagnostic utility and the predictive value of NT-pro-BNP in Kawasaki disease [6,7]. The results from these studies have also been analyzed further in a recent systematic review and meta-analysis [8].

In this issue of Indian Pediatrics, Wu, et al. [9] have evaluated the diagnostic utility of NT-proBNP and IL-17 to differentiate incomplete Kawasaki disease from other febrile infectious illnesses of childhood. IL-17 and NT-proBNP levels were estimated in 291 patients with complete Kawasaki disease, 74 patients with incomplete Kawasaki disease and 401 febrile infectious illnesses of unknown etiology. Combined with clinical criteria, when the cut-offs for IL-17 and NT-proBNP were set at 11.55 pg/mL and 225.5 pg/dL respectively, the sensitivity and specificity of differentiating incomplete Kawasaki disease from infectious illnesses reached as high as 86.5% and 94.8%, respectively.

Elevated levels of NT-proBNP are by no means specific for Kawasaki disease. The levels of NT-proBNP rise significantly in several heart ailments like congestive heart failure, acute coronary syndromes and congenital heart diseases. NT-proBNP levels are also dependent upon age. Infants less than 1 month of age tend to have higher levels than older children. Overall, it seems that the concurrent estimation of the biomarker NT-proBNP and IL-17 may serve as a useful adjunct for differentiation of Kawasaki disease, especially in its incomplete form, from other confounding infectious diseases of children.

Funding: None; Competing interests: None stated.

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