A complex case of diphtheria in a pediatric patient: complications of renal failure and myocarditis

Diphtheria remains a life-threatening infectious disease in low- and middle-income countries, particularly where immunization coverage is incomplete. Severe complications such as myocarditis and acute kidney injury significantly increase mortality. Reporting rare and complex presentations is essential to improve early recognition and management. We report the case of a 6-year-old girl who presented to the emergency department with five days of aphonia, odynophagia, progressive dysphagia, fever, confusion, and oliguria. On examination, she had cervical lymphadenopathy, pharyngeal pseudomembranes, and signs of systemic toxicity. Laboratory investigations demonstrated acute kidney injury with metabolic acidosis. Echocardiography revealed myocarditis with reduced ventricular function. The patient had incomplete vaccination against diphtheria. She was treated with diphtheria antitoxin, antibiotics, and supportive critical care. Despite aggressive management, the case illustrates the severe systemic complications of toxic diphtheria. Diphtheria is transmitted primarily via respiratory droplets and direct contact with infected lesions. Children in settings with poor vaccine coverage are particularly vulnerable to severe disease. Myocarditis and renal failure are toxin-mediated complications and are the leading causes of death. This case highlights the importance of early diagnosis, laboratory confirmation, and immediate administration of antitoxin. This case underscores the ongoing threat of diphtheria in under-immunized populations. Prompt recognition and treatment are essential to prevent fatal complications. Strengthening routine immunization programs remains the most effective strategy to reduce diphtheria-related morbidity and mortality.