All the 8 cases reported in this study were diagnosed as lung infection with mucus plugs. Among them 1 patient had consolidation as well as pleural effusion, and 5 patients had consolidation. 7 cases were infected with M. pneumoniae, while 1 case was identified as ADV infection. Mucus plugs formation was actually a manifestation of severe cilia abnormalities. Severe cilia abnormalities disrupt the mucociliary clearance, causing mucus plugs which is responsible for the development of consolidation [4]. It was reported that, when systemic inflammatory reactions are similar, the degree of local airway mucosal damage caused by M. pneumoniae and ADV may be more severe than other pathogens, and M. pneumoniae pneumonia can occur mucus plugs when local airway secretions increase and the integrity of the tube wall is damaged [8–10].
In our report, mucus plugs difficult to be sucked out were identified in all patients, which is constantly overflowing from the opening of bronchia. Histological examination of the 2 patients revealed fibrinous necrosis characterized by a large number of cellulose cells, and inflammatory exudate characterized by a variety of neutrophils and lymphocytes. Plastic bronchitis mainly occurring in childhood is a rare life-threatening disease characterized by progressive dyspnea and formation of bronchial casts, and the most common complication was respiratory failure with respiratory support [8–10], while 8 cases in our report even don’t need oxygen therapy. Histological examination of the bronchial cast by using electronic fiber bronchoscopy from 5 patients in Guangzhou province, China, diagnosed as plastic bronchitis, revealed a fibrinous exudation and necrotic material containing large quantity of neutrophils [8–9]. Therefore, we highly suspected that these mucus plugs might be the early presentation of plastic bronchitis [5].
Although the clinical manifestations of 8 patients are similar, there are so many differences among their course of disease and laboratory values. Patient 1 showed a significant elevation of CRP, PCT, WBC and Neutrophil ratio, while white blood cell count and percentage of multiple nucleated cells in bronchoalveolar lavage fluid were 316 × 106/L, 75.3%. However, Patient 4 and patient 6 showed normal CRP, PCT, WBC and Neutrophil ratio, while white blood cell count and percentage of multiple nucleated cells in bronchoalveolar lavage fluid were more than 20000 × 106/L, 80%. It was Seear and Hui who first distinguished inflammatory casts (type 1) made up of infiltrates of inflammatory cells, fibrin, and eosinophils and acellular casts (type 2) made up of mucin and rare monocytic cells, in 1997 [11]. According to Seear and Hui’s classification, considering that mucus plugs were difficult to be sucked out and fibrinous necrosis in our report, it might be type 2 cast in patient 1, It is a pity that our patient refused to accept pathologic examination. Type 1 cast could be identified in the others.
Conservative therapy, such as corticosteroids, antibiotics, mucolytic agents, bronchoscopy, chest physiotherapy, and inhalation treatment can be used in atypical pathogens pneumonia presenting as mucus plugs. We performed FOB plus BAL in all the patients and found that BAL could remove respiratory tract secretions and mucus plugs. Berlucchi et al reported that conservative therapy had been successfully used to treat a rare case of 5-year-old girl affected mucus plug infection and mucus plug formation [12]. Recently Wang et al. showed that 25 children with necrotizing pneumonia caused by refractory Mycoplasma pneumonia in China, who received FOB plus BAL, had got good outcomes [13].
Delayed macrolide antibiotics treatment, was defined as the duration of disease onset to appropriate antibiotic treatment was equal to or over the 6 days while the median duration of disease onset to appropriate antibiotic treatment was 5.6 days [14–15]. Yang el al. reported that delayed appropriate antimicrobial treatment, no matter macrolide resistance or not, was associated with more severe and/or prolonged disease, and extrapulmonary manifestations [14]. Most patients were prescribed with corticosteroids because a cell-mediated strong immune response plays an important role in the development of RMPP, and it was discovered that corticosteroids were of great benefit in improving conditions. In addition, Tamura et al. had reported several successful cases of treating RMPP using corticosteroids [13,16]. In our report, the mean duration of fever was (10.71±5.12) days in M. pneumoniae pneumonia, the median duration of M. pneumoniae pneumonia onset to appropriate antibiotic treatment was (8.43±5.16) days, and the mean total length of antibiotic therapy was (12.86 ± 3.49) days. However, the period of disease course and therapy were not as long as that of other reports [12–14]. What’s more, we suggest performing inhalation therapy using salbutamol and budesonide suspension, and before endoscopic technique, which can resolve the disease avoiding to carry out more invasive managements.