The Centers for Disease Control and Prevention (CDC)’s case definition for MIS-C is (1) an individual less than 21 years of age presenting with fever, (2) laboratory evidence of inflammation by one or more markers (such as CRP, ESR, fibrinogen), (3) evidence of clinically severe illness requiring hospitalization, with greater than 2 organ systems involved (cardiac, renal, respiratory, hematologic, GI, mucocutaneous, or neurological), (4) no other plausible alternative diagnosis, and (5) SARS-CoV-2 infection confirmed by RT-PCR, serology, or antigen testing (or, absent a positive SARS-CoV-2 test, exposure to a suspected or confirmed COVID-19 case within 4 weeks prior to symptom onset). Our patient, a previously healthy young adult woman in her mid-20’s, met these criteria with the exception of age.
Several features of our patient’s presentation raised concern for MIS-C-like illness. First, she was noted to have conjunctivitis and mucositis upon evaluation in the ED, and the cracked lips in particular were suggestive of the mucositis seen in Kawasaki’s disease. Conjunctivitis has very rarely been reported in adults with COVID-19(10), but multiple case series of MIS-C in the pediatric population have noted this clinical feature(2,3,11). Additionally, our patient had profound GI symptoms leading to hypovolemia and AKI to a creatinine of 7.7, which was fluid-responsive. While GI symptoms do occur in adults with COVID-19, they are typically less severe; by contrast, prominent GI symptoms are seen in many patients with MIS-C(4,12). Finally, our patient’s stable respiratory status was itself a feature shared by patients with MIS-C, who often lack intrinsic respiratory disease (2).
Other features were potentially compatible with MIS-C-like illness, including shock and cardiac dysfunction. Like many patients with MIS-C, our patient required treatment with vasopressors in the ICU; her shock was thought to be multifactorial including hypovolemic and cardiogenic. She had elevated troponin and BNP, but unlike many patients with MIS-C, her cardiac dysfunction was primarily right-sided. Echocardiogram showed severe right ventricular dysfunction and CT showed evidence of pulmonary vascular disease by enlarged PA without evidence of thrombus. It is interesting to speculate whether she had a COVID-19 related vasculitic process or diffuse microthrombi leading to elevated pulmonary vascular resistance and subsequent right ventricular strain. She did not have LV dysfunction, coronary aneurysms, or valvular dysfunction, as have been described in pediatric patients with MIS-C(2,13).
Several other features of our patient’s clinical presentation were less consistent with MIS-C as it has been described in the pediatric population. Her profound acute kidney injury and leukocytosis were not features described in the majority of MIS-C cases described to date(4). Additionally, her neutrophilia and lymphopenia were more consistent with typical COVID-19 findings in adults, though they have been described in cases of MIS-C as well.
In conclusion, we describe an unusual case of MISC-like illness in a young adult with COVID-19. MIS-C is an emerging and poorly understood clinical entity associated that has been described in children with COVID-19 and has features similar to Kawasaki’s disease. Children with MIS-C are increasingly treated with IVIG, aspirin, and steroids; it is not clear what if any clinical features in adults may warrant similar treatment approaches. Our patient was treated with IVIG and aspirin and improved without further cardiac involvement, but this is obviously anecdotal. Further research into COVID-19 in the young adult population is needed to better characterize the full range of clinical manifestations, and to identify potential opportunities for targeted treatment of inflammatory processes.