The clinical manifestations of diphtheria depend upon the following: (a) immune status of the patient, ( b) virulence of the bacteria, and (c) the site of the infection. Toxigenic strains (tox1) of C. diphtheriae cause:
Serious, sometimes fatal, disease in nonimmune patients.
Mild respiratory diseases in partially immune patients.
Asymptomatic colonization in fully immune individuals.
Nontoxigenic strains (tox2) cause a mild disease, such as cutaneous diphtheria.
Incubation period varies from 2 to 5 days. Sore throat, in the absence of systemic complaints, is the usual initial symptom. Fever, if occurs, is usually lower than 102°F, and malaise, dysphagia, and headache are frequently present. Respiratory diphtheria is:
· Characterized by the formation of a fibrinous pseudomem-brane on the palate, pharynx, epiglottis, larynx, or trachea and may extend to the tracheobronchial tree. The pseudo-membrane is generally a firmly adherent, thick, fibrinous, gray-brown membrane. This membrane may cause bleeding if disturbed. Respiratory distress may occur if the membrane breaks loose and occludes the airways.
· Associated with marked edema of the tonsils, uvula, submandibular region, and anterior neck (bull neck).
· Complications of respiratory diphtheria include the following:
· Myocarditis—the main complication, which may occur in as many as two-thirds of the patients.
· Circulatory collapse, heart failure, atrioventricular blocks, and dysrhythmias may also occur.
· Involvement of the cranial nerves (leading to paralysis of the soft palate with resultant difficulty in swallowing and nasal regurgitation of the fluids) and polyneuritis of the lower extremities. Recovery is complete in both cases.
Cutaneous diphtheria is generally caused by nontoxigenic strains (tox2 strains) of C. diphtheriae. The condition is an indolent nonprogressive infection characterized by a superfi-cial, nonhealing ulcer with a gray-brown membrane. The con-dition may occur at one or more sites—usually confined to the areas with previous mild trauma or bruising. Extremities are affected more often than the trunk or head. Pain, tender-ness, erythema, and exudate are the typical presentations. Respiratory tract colonization or symptomatic infection and toxic complications occur in a minority of patients with cuta-neous diphtheria. Cutaneous diphtheria may persist for weeks to months. Cutaneous diphtheria often causes no toxicity while producing natural immunity; however, it may cause epidemics in poorly immunized populations.
External ear, eye (usually the palpebral conjunctivae), and genital mucosa are the other sites of diphtheria. Rare sporadic cases of endocarditis usually due to nontoxigenic strains have been reported. Septicemia caused by C. diphtheriae is rare but is invariably fatal.