Diphtheria is an acute bacterial infection caused by a gram-positive bacillus, Corynebacterium diphtheria that makes toxins (poison). It can lead to difficulty breathing, heart failure, paralysis, and even death. CDC recommends vaccines for infants, children, teens, and adults to prevent diphtheria. Before the introduction of vaccines, diphtheria was a leading cause of childhood death around the world, including in the United States. Due to the success of the U.S. immunization program, diphtheria is now nearly unheard of in the United States. However, the disease continues to cause illness globally and there have been outbreaks reported in recent years. In 2018, countries reported more than 16,000 cases of diphtheria to the World Health Organization, and there are likely many more cases. Diphtheria rarely occurs in the United States and Western Europe, where children have been vaccinated against the condition for decades. However, diphtheria is still common in developing countries where vaccination rates are low. Diphtheria bacteria spread from person to person, usually through respiratory droplets, like from coughing or sneezing. People can also get sick from touching infected open sores or ulcers.
Pathogenesis of this infection is, that the secretions and discharges from the infected person or carrier are the main sources of infection. The infection is transmitted by contact or via droplets of secretion. The portal of entry is commonly the respiratory tract. The incubation period of the disease is 2-5 days. C. diphtheria proliferates and liberates powerful exotoxin which is the principal cause of systemic and local lesions. The exotoxin causes necrosis of the epithelial cells and liberates serous and fibrous material which forms a grayish-white pseudomembrane that bleeds on being dislodged. The surrounding tissue is inflamed and edematous. The organs principally affected by the exotoxin include the heart, kidney, and myocardium.
The onset is generally acute with fever, malaise, and headache. The child has a toxic look. The clinical features depend on the site of involvement. The commonest form is fauces/tonsillopharyngeal diphtheria in which there is redness and swelling over the fauces. The exudates coalesce to form a grayish-white pseudomembrane, which extends to surrounding areas. The cervical lymph nodes are enlarged leading to a bull neck appearance. Sore throat, dysphagia, and muffled voice are frequently present. In nasal diphtheria, there is unilateral/bilateral serosanguinous discharge from the nose and excoriation of the upper lip. In laryngotracheal diphtheria, the membrane over the larynx leads to brassy cough, stridor, and respiratory distress. Diphtheritic lesions may occasionally also be found in skin and conjunctiva. The commonest complication is respiratory failure due to occlusion of the airways by the membrane. Myocarditis generally occurs by the second week of illness and can lead to symptoms of congestive cardiac failure, arrhythmias, and sudden death. Neurological complications include: (i) palatal palsy, which occurs in the second week and is clinically manifested by nasal twang and nasal regurgitation; (ii) ocular palsy in the third week; (iii) loss of accommodation, manifested by visual blurring and inability to read; and (iv) generalized polyneuritis occurs by 3rd to 6th weeks of illness. Renal complications include oliguria and proteinuria.
There should be a high index of suspicion. Rapid diagnosis is enabled by Albert stain of a swab from the oropharynx and larynx. Culture, however, takes eight hours to become available. Faucal diphtheria should be differentiated from acute streptococcal membranous tonsillitis (patients have high fever but are less toxic and the membrane is confined to the tonsils), viral (adenovirus) membranous tonsillitis (high fever, sore throat, membranous tonsillitis with normal leukocyte count, self-limited course of 4-8 days), herpetic tonsillitis, thrush, infectious mononucleosis, agranulocytosis, and leukemia.
The patient should be isolated until two successive cultures of the throat and nose are negative for diphtheria bacillus. All contaminated articles from discharges should be disinfected. All household and other contacts should be observed carefully for the development of active lesions, cultured for C. diphtheria, and given chemoprophylaxis with oral erythromycin for 7 days or single-dose benzathine penicillin. Previously immunized asymptomatic patients should receive a booster dose of diphtheria toxoid. Those not fully immunized should receive immunization for their age.