KD, which was first described in 1967 by Dr. Tomisaku Kawasaki, is diagnosed frequently in the Asian pediatric populations. Cardiac manifestations, including coronary artery aneurysms, myocarditis, myocardial infarction, and sudden cardiac death, are the most serious complications observed in KD. However, KD can also present in the form of KDSS. Since KD is rarely seen in anyone over 9 years of age(7), after the peak age of onset, it is not often considered and is probably underdiagnosed to some degree. Interestingly, age > 10 years has been reported as one of the risk factors for progression to KDSS(8). It is crucial to be cognizant of the potential occurrence of KDSS, since prompt recognition and management are necessary to ensure optimal patient outcomes (9).
Although the specific etiology of profound hypotension in KDSS is still not fully understood, there are hypotheses supporting vasculitis with capillary leakage, myocardial function defect, and dysregulation of cytokines at a systemic level, resulting in cardiogenic and/or distributive shock (3, 10). In our case, the boy had severe vascular leakage and hypoalbuminemia, with pleural effusions and ascites. In our opinion, the shock was probably due to a significant inflammatory state and vascular leakage, as no sign of remarkable cardiac dysfunction on echocardiography showed. Natterer et al also described three cases of KDSS present with normal myocardial function(5). However, the significant elevation of BNP still suggested some myocardial inflammation. Undeniably, myocardial dysfunction in our case may have been underestimated own to timely application of vasoactive agonists, and subsequent appropriate management of KDSS.
Our case illustrates that, in the pediatric population, when children with shock or hypotension require admission to the PICU and fail to respond to antibiotic therapy, it is crucial to consider the possibility of KDSS, even if the diagnostic criteria for KD was not initially fulfilled. In addition, it is important to adopt a comprehensive diagnostic approach that beyond traditional criteria. Timely recognition and appropriate management are crucial to optimize patient outcomes in these intractable clinical scenarios (10–13).
In our case study, a twelve-year-old boy exhibited persistent fever, bilateral non-purulent conjunctivitis, edematous limbs, unresponsive shock, low levels of albumin, significantly elevated levels of CRP. Despite the presence of these clinical indicators, the diagnosis of KDSS was not definitively confirmed until a subsequent phase of the illness. The delayed diagnosis is due to the considerable overlap in clinical features between TSS and KDSS.
For children with KD, multiple systems including the respiratory system can be affected(14). Common pulmonary manifestations mainly include bronchopneumonia, hydropneumothorax, and pleural effusion. A few studies have reported that KD may appear secondary to lung consolidation, which often occurs due to Streptococcus, Staphylococcus, Mycoplasma, EB virus, coronavirus, or parvovirus infection(15). Thus, in the current case, it was essential to identify whether lung consolidation appeared secondary to KDSS or TSS.
Considering that, the blood cultures were consistently negative, the transudate did not contain bacterial infection, moreover, lung consolidation appeared during KDSS progression. Thus, pathological changes observed in the lung were considered to be related to KD. In addition, cardiac valve regurgitation, which was seen in our case might be another discriminating factor between KDSS and TSS, since previous studies have found that echocardiographic abnormalities including cardiac valve regurgitation were considerably more common among patients with KDSS(16–17).
In terms of treatment, despite fluid resuscitation and maintenance of hemodynamic stability are similar, the course of disease evolution between KDSS or TSS are different. Generally speaking, multiple organ dysfunction in KDSS was less severe and mostly transient. Meanwhile, shock associated with KD can be controlled relatively easily by vasoactive agent. On the contrary, once the blood pressure drops in septic shock or TSS, the condition is often very critical, the incidence of multiple organ failure is high, and the mortality is significantly increased. Specific antibiotics and glucocorticoid are used to treat TSS, which still leads to high mortality rates (up to 44%) after treatment(18). For KDSS, IVIG should be administered as soon as possible to achieve a good prognosis, while the use of antibiotics is not required. When unusual pulmonary changes similar to bacterial infection appear, KDSS and TSS should be identified based on monism. For our case, according to the principles of KD therapy, consolidation was absorbed rapidly, and the course of treatment was much shorter than the cure course of consolidation in the bilateral lungs caused by a bacterial infection, which further confirmed the diagnosis of KD-related pulmonary changes.
Our case highlights that children with KD may present with a toxic shock-like illness. And it is essential to promptly recognize and remain vigilant for the manifestation of KDSS. Early detection enables timely initiation of treatment, which can have a profound impact on patient outcomes. To the best of our knowledge, this represents the first documented case of KDSS with polyserous effusion reported globally. This underscores the rarity of such occurrences and emphasizes the importance of further research and continued awareness of this complex clinical entity.