Snapshot A 4-year-old girl presents to the emergency room for a fever and sore throat. She recently visited Thailand for 2 months with her parents and had just flown back a couple of days ago. Her parents report that she has not had any of her recommended immunizations, as they have traveled all over the world. On physical exam, there is a grayish-white membrane covering her soft palate. When irritated by a tongue depressor, the membrane oozes with blood. She also has marked cervical lymphadenopathy and edema of the neck. She is immediately admitted for monitoring, antibiotics, and antitoxin. Introduction Classification Corynebacterium diphtheriae aerobic gram-positive rod produces diphtheria toxin transmission respiratory droplets Epidemiology demographics rare in the US more common in developing countries Pathogenesis diphtheria exotoxin inactivates elongation factor (EF-2) via ADP-ribosylation inhibits protein synthesis, causing necrosis in respiratory, cardiac and central nervous system tissue affects mucous membranes, especially the respiratory tract exotoxin is encoded by β-prophage Associated conditions diphtheria cutaneous diphtheria ulcerative lesions or cellulitis can occur independently of respiratory diphtheria Prevention DTap vaccine vaccine against diphtheria, tetanus, and pertussis 5 doses before school-age, completed by 4-6 years of age Tdap vaccine booster vaccine at 11-12 years of age should also be given to pregnant mothers and those around them Td vaccine tetanus and diphtheria toxoid vaccine at 10-year intervals Prognosis symptoms are insidious mortality is higher in young children, but generally good with prompt treatment Presentation Symptoms fever sore throat malaise may have a croup-like cough Physical exam pseudomembranous pharyngitis gray or bluish white membrane seen on soft palate, tonsils, or back of the throat bleeds easily if irritated develops 2-3 days after symptoms severe cervical lymphadenopathy “bull neck” myocarditis arrhythmias Studies Bacterial culture gram-positive rods with blue and red granules (metachromically) seen on culture cysteine-tellurite agar (appears as black colonies) Löffler medium positive Elek test for diphtheria toxin Making the diagnosis most cases are clinically diagnosed and confirmed with a culture Differential Streptococcal pharyngitis distinguishing factor no pseudomembrane on mucous membranes Treatment Medical diphtheria antitoxin indication all patients antibiotics indications all patients drugs erythromycin penicillin G Complications Airway compromise from soft tissue swelling Heart failure from myocarditis Secondary bacterial infection (e.g., pneumonia)