A white membrane is visible covering the tissues including the uvula, palate, tonsils, and pharynx. Attempts to remove this membrane, result in bleeding. Partially immunized patients may have incomplete presentations such that the white membrane does not form. Laryngeal diphtheria results from downward extension of pharyngeal diphtheria. Laryngeal involvement is characterized by croup-like symptoms such as stridor, drooling, hoarseness and a barking cough.
Airway obstruction is more likely to progress to a severe degree.
The trachea and bronchi may also be involved. However, the clinical features, especially the appearance of the pharynx is usually different. In severe cases of laryngeal diphtheria, a membrane may be visible on the lateral neck radiograph and the degree of subglottic edema seen radiographically is more severe. View membranous croup radiograph. This radiograph shows subglottic narrowing.