infectious diseases
Diphtheria
Symptoms and Signs of Diphtheria
Symptoms of diphtheria vary depending on Where the infection is Whether the strain produces toxin Most respiratory infections are caused by toxigenic strains. Cutaneous infections are caused by toxigenic and nontoxigenic strains. Toxin is poorly absorbed from the skin; thus, toxin complications are rare in cutaneous diphtheria. After an incubation period, which averages 5 days, and a prodromal period of between 12 and 24 hours, patients develop mild sore throat, dysphagia, low-grade fever, and tachycardia. Nausea, emesis, chills, headache, and fever are more common among children. If a toxigenic strain is involved, the characteristic membrane appears in the tonsillar area. It may initially appear as a white, glossy exudate but typically becomes dirty gray, tough, fibrinous, and adherent so that removal causes bleeding. Local edema may cause a visibly swollen neck (bull neck), hoarseness, stridor, and dyspnea. The membrane may extend to the larynx, trachea, and bronchi and may partially obstruct the airway or suddenly detach, causing complete obstruction. If a large amount of toxin is absorbed, severe prostration, pallor, tachycardia, stupor, and coma may occur; toxemia may cause death within 6 to 10 days. Mild disease with a serosanguineous or purulent discharge and irritation of the external nares and upper lip occur in patients who have only nasal diphtheria. Toxigenic strains ofCorynebacterium diphtheriaemay cause a thick pharyngeal exudate. The exudate is dirty gray and is tough, fibrinous, and adherent to the mucosae. Image courtesy of the Centers for Disease Control and Prevention. In acute nasopharyngeal diphtheria, local edema may cause a visibly swollen neck (bull neck). Image courtesy of the Public Health Image Library of the Centers for Disease Control and Prevention. The scaling rash of cutaneous diphtheria, as seen on the neck in this image, may be indistinguishable from more common skin conditions, such as eczema, psoriasis, and impetigo. Image courtesy of the Public Health Image Library of the Centers for Disease Control and Prevention. In a few cases, cutaneous diphtheria may undergo central ulceration; occasionally, a grayish membrane forms. Image courtesy of the Public Health Image Library of the Centers for Disease Control and Prevention. Skin lesions usually occur on the extremities and are varied in appearance, often indistinguishable from chronic skin conditions (eg, eczema, psoriasis, impetigo). A few patients have nonhealing, punched-out ulcers, occasionally with a grayish membrane. Pain, tenderness, erythema, and exudate are typical. If exotoxin is produced, lesions may be numb. Concomitant nasopharyngeal infection occurs in 20 to 40% by direct or indirect inoculation with the organism, often from preexisting chronic skin lesions. The main complications of diphtheria are cardiac and neurologic. Myocarditis None Nervous system toxicityis uncommon (about 5%) and limited to patients with severe respiratory diphtheria. The toxin causes a demyelinating polyneuropathy that affects cranial and peripheral nerves. The toxic effects usually begin during the 1st week of illness with loss of ocular accommodation and bulbar palsy, causing dysphagia and nasal regurgitation. Peripheral neuropathy appears during the 3rd to 6th week. It is both motor and sensory, although motor symptoms predominate. The diaphragm may become paralyzed, sometimes causing respiratory failure. Resolution occurs over many weeks. Autonomic dysfunction in the form of loss of vasomotor tone (tachycardia, arrhythmias, and arterial hypotension) is also a complication of diphtheria. In severe cases, acute renal failure may occur because the toxin damages the kidneys. Overall mortalityis 3%; it is higher in those with any of the following: Delayed presentation Acute renal failure Myocarditis Age < 15 years or > 40 years 