Multisystem inflammatory syndrome in children (MIS-C) presenting with valvulitis, myocarditis, and QTc prolongation: A case report from Saudi Arabia.

Rationale: This case report highlights the complex clinical course and successful multidisciplinary management of a pediatric patient with multisystem inflammatory syndrome in children (MIS-C), who posed clinical dilemma at presentation. It underscores the ongoing clinical relevance of MIS-C as a post-Coronavirus disease 2019 sequelae and emphasizes the importance of maintaining a high index of suspicion for MIS-C in pediatric differential diagnoses, especially when symptoms overlap with other common conditions.

Patient Concerns: An 11-year-old previously healthy Saudi girl presented with gastrointestinal symptoms initially suggestive of acute appendicitis. Her condition rapidly deteriorated with signs of cardiovascular compromise.

Diagnoses: Surgical exploration confirmed a perforated appendix. Cardiac workup revealed elevated troponin levels, corrected QT interval prolongation (500 ms), ST-segment changes, and echocardiographic evidence of mitral and aortic regurgitation with reduced ejection fraction, leading to a diagnosis of MIS-C fulfilling both Centers for Disease Control and Prevention and World Health Organization criteria. Schwartz et al's criteria are widely accepted for diagnosing long QT syndrome, which guided our interpretation of the corrected QT interval prolongation observed in this case. According to the Centers for Disease Control and Prevention, MIS-C is defined by a constellation of symptoms occurring in individuals under 21 years with recent severe acute respiratory syndrome coronavirus 2 infection or exposure.

Interventions: Management included intravenous immunoglobulin, corticosteroids, inotropes, diuretics, aspirin, and broad-spectrum antibiotics, coordinated by a multidisciplinary care team.

Outcomes: The patient experienced full cardiac recovery, confirmed through serial electrocardiogram and echocardiography over 1 year.

Lessons: This case underscores the importance of recognizing MIS-C in children presenting with atypical symptoms such as abdominal pain. Timely diagnosis and early multidisciplinary intervention are essential to prevent serious cardiac complications.