Neonatal Multisystem Inflammatory Syndrome (MIS-N): The First Case Report in Thailand

Cases of multisystem inflammatory syndrome in children (MIS-C-like disease), have rarely been reported in neonates. A 33-week gestational age twin B female neonate presented with respiratory distress, tachycardia, and abdominal distention at 15 days of age. Echocardiogram found reduced left ventricular ejection fraction to 33%. Cardiac enzyme levels were all elevated: creatine kinase-MB 6.1 ng/mL (normal 0–4.5 ng/mL), troponin-T 170 ng/L (normal < 14 ng/L) and NT-proBNP > 35,000 pg/mL (normal 250.0 to 3987.0 pg/mL). Multiplex PCR of nasopharyngeal swab material was negative for respiratory pathogens. Serological tests revealed negative anti-spike SARS-CoV-2 IgM but positive anti-nucleocapsid SARS-CoV-2 IgG in both the mother and the patient. The mother provided a history of COVID-19 during pregnancy at 19 weeks gestation. The patient was diagnosed with neonatal multisystem inflammatory syndrome (MIS-N) and successfully treated with intravenous immunoglobulin (two doses of 1 gm/kg/dose) and methylprednisolone (2 mg/kg/day for 5 days then tapered off). She later developed coronary vessel (LMCA and RCA) dilation. The non-identical twin A did not develop MIS-N, suggesting a role of host genetic background. Newborn infants born to SARS-CoV-2-infected mothers at any time during pregnancy should be closely monitored for MIS-N. The optimal treatment approaches to this syndrome and the prognosis require further study.