Pediatric acute laryngotracheobronchitis is an acute diffuse inflammation of the upper and lower respiratory tracts. It is more commonly seen in children under 2 years of age and can develop as a complication of pediatric acute laryngitis, with a higher incidence in winter.
Etiology
This condition often occurs during flu epidemics and is generally believed to be related to the prevalence of influenza. It usually arises from influenza infection, with subsequent bacterial involvement of the trachea and bronchi. The lower temperatures in winter contribute to respiratory infections. In children, the smaller respiratory tracts, immature immune systems, and weak coughing ability make them more susceptible to this condition.
Pathology
The mucosa of the larynx, trachea, and bronchi shows diffuse congestion, with the subglottic loose connective tissue being the most prominently affected. The infection progresses downward to the trachea and bronchi, initially affecting epithelial cells and cilia, leading to mucosal congestion, swelling, and inflammatory infiltration. The submucosa becomes involved, resulting in increased glandular secretion, transitioning from serous to mucoid. Severe infections can cause necrosis of the mucosal epithelial cells and fibrinous exudation, mixing with respiratory tract secretions to form thick, gelatinous clumps containing mucus, fibrin, polymorphonuclear leukocytes, and desquamated epithelial cells.
In severe cases, necrosis of the mucosal epithelium and fibrin exudation result in the formation of pseudomembranes or crusts. These thick secretions, pseudomembranes, or crusts can block the bronchi, leading to pulmonary emphysema or atelectasis below the site of obstruction.
Thick pseudomembranes can reduce the bronchial lumen by more than 50%. These pseudomembranes may occur in sheets, cylindrical shapes, or completely occlude terminal bronchioles. Because they are difficult to cough out, they may detach and behave like foreign bodies in the tracheal lumen, requiring bronchoscopic removal. Severe cases may necessitate multiple procedures to repeatedly clear pseudomembranes and crusts from the airway.
Clinical Manifestations
The presentation typically includes features of acute laryngitis accompanied by signs of tracheal and bronchial involvement, with more severe systemic symptoms. After exposure to cold or contracting influenza, the child initially develops an irritating cough, which progresses to inspiratory dyspnea. High fever, lethargy, pallor, and rapid, weak pulses often suggest systemic intoxication. If dry crusts or pseudomembranes form in the trachea and bronchi, mixed inspiratory and expiratory respiratory difficulty may occur, accompanied by biphasic stridor.
Nocturnal exacerbations often occur, potentially related to laryngeal spasms triggered by the accumulation of secretions at the glottic cleft during sleep.
Chest auscultation may reveal both dry and wet crackles in the lungs. Chest X-rays may show increased pulmonary markings, pulmonary emphysema, and signs of atelectasis.
Diagnosis
The diagnosis primarily relies on the clinical presentation. The child exhibits signs of both acute laryngitis and tracheobronchitis. In children under 3 years of age, particularly after a high fever or infectious disease, the initial symptoms of laryngeal obstruction followed by lower respiratory tract obstruction raise strong suspicion of this condition. Findings during physical examination, such as biphasic respiratory difficulty and stridor, along with reduced, coarse breath sounds or the presence of dry rales and wheezing, further support the diagnosis.
Flexible (electronic) bronchoscopy reveals congested and swollen mucosa below the glottis, most severe in the subglottic area. The tracheal and bronchial mucosa also appear red and swollen, obscuring normal tracheal rings. Large amounts of secretions, crusts, or pseudomembranes can be observed within the lumen.
Treatment
Symptomatic Treatment
Managing airway obstruction is the primary treatment goal. If signs of laryngeal obstruction are present or secretions in the lower respiratory tract cannot be expelled, early tracheotomy facilitates the removal of thick lower respiratory tract secretions. If crusts or pseudomembranes cannot be suctioned out of the lower airways, timely bronchoscopy is recommended.
Etiological Treatment
Adequate doses of antibiotics are used to control infections. Corticosteroids are administered early to reduce laryngeal edema and inflammation throughout the respiratory tract.
Supportive Therapy
Adequate nutritional support, maintenance of water and electrolyte balance, and protection of cardiac function are emphasized. The treatment environment is optimized with an appropriate temperature (22–24°C) and relative humidity (40–60%).