Fever and Diarrhea as the Only Symptoms of Multisystem Inflammatory Syndrome in Children

Dear Editors:

We would like to congratulate Miller et al¹ on their article about multisystem inflammatory syndrome in children (MIS-C) and express our gratitude because it helped us to establish a diagnosis in our patient. Reports about MIS-C published so far come from countries with particularly high coronavirus disease (COVID-19) prevalence1, 2, 3 and the majority of described cases had severe course with frequent progression to shock. However, MIS-C may occur in any country touched by the COVID-19 pandemic and it is likely that it may present in various forms, ranging from toxic shock to much milder “fever and inflammation” variant.² We want to present a case of a 14-year-old boy, who presented with fever and diarrhea only, but fulfilled the MIS-C case definition,⁴ and had insidious, but apparent cardiac involvement.

We admitted the boy on the day 5 of fever up to 41˚C, with progressive lethargy. The only associating symptoms were abdominal pain and one episode of vomiting. The boy's father underwent febrile infection with anosmia 6 weeks earlier and tested positive for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) IgM and IgG.

On admission, the boy seemed well, with normal vital signs. On physical examination, the abdomen was soft, but painful in the right iliac pit. Laboratory evaluation revealed lymphopenia 630/μL, hemoglobin 12 g/dL, platelets 180 × 10³/μL, increased C-reactive protein 20.6 mg/dL, and ferritin 277.7 ng/mL. Despite having no cardiovascular symptoms, considering possible MIS-C, cardiac injury markers were obtained: N-terminal pro-brain natriuretic peptide (NT-pro-BNP) was 275 pg/mL and troponin 19.2 ng/L. In the hospital, the boy developed watery diarrhea. Microbiological stool tests were negative. A nasopharyngeal polymerase chain reaction test for SARS-CoV-2 was negative, whereas IgG for COVID-19 was positive. The boy received supportive treatment with oral fluids and antipyretics. Fever resolved on day 7, but cardiac markers increased: troponin 232 ng/L, NT-pro-BNP 1764 pg/mL. A chest radiograph, electrocardiography, and echocardiography revealed no abnormalities. Troponin and NT-pro-BNP concentrations normalized over the next days.

Despite the relatively low prevalence of COVID-19 in Poland, MIS-C has occurred in our country. We present the first, to our knowledge, report of a benign course of MIS-C, clinically involving only the gastrointestinal tract.

The patient's clinical presentation suggested acute bacterial diarrhea, but known SARS-CoV-2 exposure with lymphopenia and surprisingly elevated C-reactive protein levels warranted cardiologic evaluation, revealing concomitant heart involvement. This finding is particularly important because the risk for developing coronary artery aneurysms in the course of MIS-C does not seem to correlate with disease phenotype or severity.² The awareness of MIS-C among clinicians, raised by reports from countries with high COVID-19 prevalence, is fundamental for prompt diagnosis and appropriate approach to such patients in countries where COVID-19 is not as prevalent.

In conclusion, during the COVID-19 pandemic, children with fever and acute diarrhea must be carefully observed for possible heart sequelae.