Clinical characteristics
All patients were healthy previously, and the average age at the diagnosis was 36 months. The sex distribution was eight males (67%) and four females (33%). The racial/ethnic was Han. During the initial acute lower respiratory tract infection, adenovirus antigen was positive in four individuals by testing nasopharyngeal secretions, mycoplasma pneumoniae was identified in four patients and measles virus in one patient by serum IgM antibody tests, and the etiology was unknown in two patients. In addition, one patient was infected with both adenovirus and mycoplasma pneumoniae (Table 1). The diagnosis of PIBO was made on the basis of the clinical and radiographic findings. The patients presented with wheezing, cough, dyspnea, exercise intolerance, and frequent respiratory illness. Physical examination findings were persistent moist crackles, extensive wheezing and hypoxemia. In all twelve patients, HRCT scans demonstrated mosaic perfusion pattern, air trapping and bronchial wall thickening. In one patient, bronchial dilation was showed (Figure 1A and B).