Pediatric plastic bronchitis: A case report and literature review

1. Introduction 

Plastic bronchitis is an unusual, potentially fatal condition characterized by the formation of extensive inspissated mucofibrinous endobronchial casts that mimic the three-dimensional architecture of the tracheobronchial tree [1], [2]. It is the cohesiveness, consistency, and notoriously difficult bronchoscopic removal that delineates this condition from ordinary mucus plugging [3].

Patients may present with expectoration of these casts or they may be found at bronchoscopy or in a surgical specimen. Conditions associated with plastic bronchitis include congenital heart disease, especially patients with Fontan physiology (diversion of systemic venous return to the pulmonary circulation), various pulmonary disorders including asthma and cystic fibrosis, as well as other conditions such as sickle cell anemia [1]. The pathogenesis is unclear and may represent a final common pathway to the disorder.

The treatment for plastic bronchitis varies from medical treatment with corticosteroids to various inhaled lytic agents, bronchoscopy, and potentially other surgical treatments.

2. Case 

A two-year-old previously healthy girl presented with a three-day history of barky cough, low-grade fevers, and progressive respiratory distress. She had a history of subclinical asthma, but no other underlying disorders. On physical examination she was in moderate respiratory distress requiring supplemental oxygen by facemask, was tachypnic, had sternal retractions, and decreased breath sounds in the right upper and middle lobes. A chest X-ray showed a hazy right upper lobe lung field with suggestion of obstruction at the area of the bronchus intermedius (Fig. 1).

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Fig. 1. PA CXR showing a hazy right upper lobe lung field with suggestion of obstruction at the area of the bronchus intermedius.

The decision was made to take the patient to the operating room for bronchoscopy to rule out foreign body. Instead, tenacious bronchial mucus casts were removed from the right upper lobe bronchus and bronchus intermedius. Histopathology demonstrated that the casts were composed of dense fibrinous debris with an eosinophil-rich, mixed inflammatory infiltrate (Fig. 2).

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Fig. 2. Histopathology demonstrating that the casts were composed of dense fibrinous debris with an eosinophil-rich, mixed inflammatory infiltrate.

Postoperatively, the patient's clinical condition rapidly improved and she was discharged to home on postoperative day two. The patient has not had any recurrences to date and remains on as needed treatment with albuterol for mild asthma. A sweat choride test was negative.

3. Discussion 

Historically, the first decriptions of plastic bronchitis date back to Galen (AD 131-200) in which he described “venae arteriosae expectorantii,” literally “expectorated arteries and veins.” Morgagni later postulated that these structures consisted of inspissated bronchial mucus [4]. The characteristic branching mucoid bronchial casts once referred to as fibrinous bronchitis or pseudomembranous bronchitis came to be uniformly known as plastic bronchitis in the 20th century [5].

Demographically, plastic bronchitis affects all age groups but is more freqeuntly reported in children, average age of six years in a relatively large review [1]. Males and females tend to be equally affected according to most reports, but Eberlein et al. suggested a female predominance [1], [5], [6]. The true prevalence of plastic bronchitis in unkown.

Clinical presentation varies from mild symptoms to life threatening disease. The hallmark is expectoration of branching bronchial casts or discovery of these on bronchoscopy. Typically patients present with dyspnea, coughing, wheezing, and respiratory distress, occasionally with fevers or chest pain [3], [7]. Radiographic evaluation typically shows atelectasis and infiltrates on the ipsilateral side, often with hyperinflation of the contralateral side. CT scanning may allow for visualization of impacted casts within the major airways [8]. Diagnosis may be made from previously expectorated casts or on bronchoscopy.

The pathogenesis of plastic bronchitis is unclear. Several theories have been proposed including increased pulmonary venous pressure, increased inflammatory response, trauma to bronchial lymphatic channels, and ischemia of the bronchial tree [3], [7], [9]. Plastic bronchitis may represent a final common pathway to a variety of insults to the bronchial tree.

Seear et al. have proposed a two-type classification scheme based on cast histology as shown in Table 1. Type I or inflammatory casts are composed of fibrin with a dense eosinophilic infiltrate. These casts tend to be associated with broncho-pulmonary disorders. Patients with type I casts often present with a more acute clinical presentation. Type II or acellular casts consist maily of mucin. Type II casts occur primarily in children following the repair of cyanotic congenital heart defects and also are seen in cases of idiopathic plastic bronchitis. Patients with type II casts often have a chronic or recurrent presentation [10].

Table 1. Classification schemes and associated conditions.

A more recent classification scheme divides plastic bronchitis into 4 etiological groups related to associated condition as shown in Table 1. Structural congenital heart disease is associated with acellular, mucinous casts. Asthma and atopic diseases demonstate abundant eosinophils, Charcot-Leyden crystals, fibrin, and neutrophils. Lymphatic disorders have chylous casts sometimes containing fibrin. Sickle cell anemia is associated with casts composed of fibrinous material with pigmented histiocytes in the surrounding fluid [11].

Conditions associated with plastic bronchitis include cyanotic congenital heart disease, asthma, lymphatic disorders, sickle cell anemia, pulmonary infections, and lymphoma. In a review of 42 cases of pediatric plastic bronchitis, Brogen et al. noted that 40% of patients had underlying cardiac defects, 31% had asthma or allergic disease, and 29% had other diseases as shown in Table 1. They noted that an overall mortality rate of 16%, increasing to 29% in patients with cardiac defects. Similarly, life-threatening events were also higher in patients with cardiac defects. Likewise, mortality was higher in patients with type II casts (28% vs 6%), but this did not reach statistical significance [1].

Moser et al. reviewed the prevalence, clinical features, and role of bronchoscopy in patients with plastic bronchitis during the acute chest syndrome (ACS) of sickle cell disease. They noted that pediatric inpatients in their review with ACS who underwent bronchoscopy, plastic bronchitis was diagnosed in 21 of 29 episodes (72%) [9].

Treatment stratagies range from medical treatment with corticosteroids to various inhaled lytic agents, bronchoscopy, and potentially other surgical treatments. Corticosteroids have typically been used for inflammatory type I casts, but have also been used effectively after Fontan operation [12]. There have been several reports of various inhaled agents used including heparin, tissue plasminogen activator, acetylcysteine, macrolide antibiotics, urokinase, and DNAse [13], [14], [15], [16], [17]. After initial respiratory stabilization and medical treatment of underlying disease, bronchosopic removal is routinely practiced and may need to be repeated for continued bronchopulmonary toilet. Bronchoscopy is also indicated in cases of plastic bronchitis associated with congenital heart disease, which may be recurrent. The challenge in bronchoscopy seems to be in removal of these casts that can be too thick to suction and too soft to grab with forceps leading others to try massive bronchopulmonary lavage [18]. Other treatments include cardiac procedures designed to improve cardiac output in congential heart disease patients and also Extracorporeal Membrane Oxygenation as a possible adjunct for rapid clinical deterioration unresponsive to standard therapy.

Shah et al. entertained the idea of thoracic duct ligation as a potential treatment. They theorized that high intrathoracic lymphatic pressures with lympho-alveolar fistulas were the cause recurrent plastic bronchitis in 2 Fontan patients resistant to medical therapy. They reported success in both patients for up to two years follow up. They suggest that thoracic duct ligation provides a surgical cure for plastic bronchitis by decreasing intrathoracic lymphatic pressure and flow [19]. While this treatment was successful in these 2 Fontan patients, Nayar et al. concluded that patients with type I casts after congenital cardiac surgery may not benefit from thoracic duct ligation [20].

4. Conclusions 

Our patient falls into the category of plastic bronchitis associated with pulmonary disorders, type I cast formation, and better clinical prognosis. Her clinical course may parallel others with similar underlying causes.

Plastic bronchitis is relatively uncommon, but it is a potentially life threatening condition. This has been underscored in a recent report of two fatal cases presented this year by Cajaiba et al. [3]. Prompt diagnostic and therapeutic bronchoscopy is warranted in these patients. Children with cardiac defects have a poorer prognosis and may be at the end of a spectrum of disease.