The most concerning of the five cases in terms of possible MIS-C, Dr. Dean said in an interview, was that of a 12-year-old boy who had fever for 6 days in association with headache, eczematous rash, dry lips, and conjunctivitis. Laboratory tests showed a mildly elevated C-reactive protein level, hyponatremia, and thrombocytopenia, as well as sterile pyuria and mildly elevated prothrombin time. He was treated empirically with doxycycline, and his fever resolved over the next 24 hours.
An echocardiogram at initial evaluation, however, revealed mild dilation of the left anterior descending and right coronary arteries, which led to the administration of intravenous immunoglobulin and aspirin for atypical KD, in contrast to MIS-C. The authors postulated that mild cardiac involvement in disorders other than MIS-C and KD may be underrecognized.
The lesson from these cases, Dr. Dean and associates concluded, is that hospitalists must maintain a wide differential diagnosis when assessing a child with prolonged fever and evidence of systemic inflammation. The CDC stipulates that a diagnosis of MIS-C requires the absence of a plausible alternative diagnosis.
In addition to common viral, bacterial, and noninfectious disorders, a range of regional endemic rickettsial and parasitic infections must be considered as alternative diagnoses to MIS-C. “Many of these diseases cannot be reliably differentiated from MIS-C on presentation, and as community exposure to SARS-CoV-2 grows, hospitalists should be prepared to admit febrile children with evidence of systemic inflammation for brief observation periods to evaluate for MIS-C,” Dr. Dean’s group wrote. In this context, however, empiric treatment for common or even uncommon infectious diseases may avoid overdiagnosis and overtreatment of MIS-C as well as improve patient outcomes.
“We do have specific MIS-C guidelines at our institution,” Dr. Dean said, “but like all institutions, we are dealing with the broad definition of MIS-C according to the World Health Organization and the CDC, which is really the takeaway from this paper.”
More difficult differentiation
Both groups of authors pointed out that, as SARS-CoV-2 spreads throughout a community, a higher percentage of the population will have positive results on antibody testing, and such results will become less useful for differentiating between MIS-C and other conditions.
Despite these series’ cautionary lessons, other experts point to the critical importance of including MIS-C early on in the interest of efficient diagnosis and therapy. “In the cases cited, other pathologies were evaluated for and treated accordingly,” said Kara Gross Margolis, MD, AGAF, an associate professor of pediatrics in the division of pediatric gastroenterology, hepatology, and nutrition at Morgan Stanley Children’s Hospital,New York. “These papers stress the need for a balance that is important, and all potential diagnoses need to be considered, but MIS-C, due to its potential severe consequences, also needs to be on our differential now.”
In her view, as this new high-morbidity entity becomes more widespread during the pandemic, it will be increasingly important to keep this condition on the diagnostic radar.
Interestingly, in a converse example of diagnostic clouding, Dr. Gross Margolis’s group reported (Gastroenterology. 2020 Oct;159:1571-4.e2) last year on a pediatric case series in which the presence of gastrointestinal symptoms in children with COVID-19–related MIS-C muddied the diagnosis by confusing this potentially severe syndrome with more common and less toxic gastrointestinal infections.
According to Dr. Smart, although the two reports don’t offer evidence for a particular diagnostic practice, they can inform the decision-making process. “It may be that we will have enough evidence shortly to say what the best practice is regarding diagnostic evaluation of possible MIS-C cases,” he said. “Until then, we must remember that common things occur commonly, even during a global pandemic.”
Neither of the two reports received any specific funding. The authors disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.