A 7-yr-old boy was admitted to a local hospital because of a 1-day history of cough, fever and aggravating dyspnea on November 15, 2009. Real-time polymerase chain reaction (RT-PCR) for H1N1 was positive, and the patient was treated with oral oseltamivir. On physical examination, breath sounds were decreased in the left lung. A chest radiograph revealed complete atelectasis in the left lung and over-inflation of the right lung (Fig. 1A). A chest computed tomography (CT) scan showed left main bronchial obstruction with low attenuated materials and atelectasis of the left lung (Fig. 2A, C). Laboratory studies revealed as hemoglobin of 13.2 g/dL, white blood cell count of 10,600/µL (polymorphonuclear cells, 95.8%; lymphocytes, 1.5%; and eosinophils, 2.7%), and platelet count of 318,000/µL. The C-reactive protein level was 2.3 mg/dL, erythrocyte sedimentation rate was 6 mm/hr, and antistreptolysin O titer was 105 IU/mL. Anti-mycoplasma antibody was negative. Total IgE exceeded 3,000 IU/mL. Electrolytes, and liver and kidney function tests were in the normal range. The arterial blood gas analysis was as follows: pH 7.42, pCO₂ 34.5 mmHg, pO₂ 67.5 mmHg, and HCO₃ 22.3 mmHg. Gram-stain, acid fast stain, potassium hydroxide mounts, Mycobacterium tuberculosis culture, culture for other sputum bacteria, and fungus culture of sputum were negative. After supplying O2 via an oxygen mask, dyspnea was relieved and aeration of the left lung on the chest radiograph was also improved. The patient received mucolytics, chest physiotherapy, and antibiotics. Although amoxicillin-clavulanate was chosen due to the patient's history of allergy to ceftriaxone, an urticarial rash developed after amoxicillin-clavulanate administration. The rash subsided with antihistamine use. On day 4 following admission, the patient underwent a bronchoscopy because of aggravating dyspnea. The bronchoscopy showed total obstruction of the left main bronchus by a rubbery cast. The chest radiograph and CT scan after extraction of the cast showed the left lung recovered with good aeration (Fig. 2B, D). The patient was discharged 12 days after admission.

The same patient was referred to the emergency department of our hospital because of acute respiratory distress 5 months later after the first attack. The patient was hospitalized at a local hospital 2 days before because of a 4-day history of cough and mild fever. The patient was managed with antibiotics and mucolytics under the diagnosis of pneumonia. However, shortness of breath was aggravated suddenly and a chest radiograph showed total atelectasis of the left lung (Fig. 1B). On arrival at our emergency room, the patient presented with tachypnea, deceased breath sounds in the left lung field, and chest retraction. SpO₂ was 85% on 100% face mask oxygen, and the arterial blood gas analysis was as follows: pH 7.33, pCO₂ 37.9 mmHg; pO₂ 68.8 mmHg, and HCO₃, 19.5 mmHg. The body temperature was 36.7℃, pulse rate was 164/min, respiratory rate was 48/min, and blood pressure was 100/60 mmHg. The patient was intubated and mechanical ventilation was applied in the emergency room due to respiratory failure. Laboratory studies revealed hemoglobin of 14.4 g/dL, white blood cell count of 23,200/µL (polymorphonuclear cells, 95.4%; lymphocytes, 2.0%; and eosinophils, 0.4%), and platelet count of 357,000/µL. The C-reactive protein level was 5.2 mg/dL, erythrocyte sedimentation rate was 11 mm/hr, lactate dehydrogenase was 941 U/L, and antistreptolysin O titer was 85 IU/mL. Urine pneumococcal antigen and the anti-mycoplasma antibody were negative. The rapid nasal swab influenza antigen test was negative for influenza A but positive for influenza B virus. RT-PCR for H1N1 and influenza B virus were negative and positive, respectively. Shell vial culture for influenza A, parainfluenza, adenovirus, and respiratory syncytial virus were all negative, but only for influenza B was positive. To exclude allergic bronchial fungal disease, we also did tests for fungal infection. Each fungus culture with specimens obtained from endotracheal aspiration and bronchial lavage was negative. Aspergillus antigen and antibody immunoglobulin G were negative. Electrolytes, liver and renal function tests were within normal range. A chest CT scan demonstrated low attenuated materials filling the left main and lobar bronchi, and total consolidation or atelectasis in the left lung. An electrocardiogram and echocardiography were normal. On the admission day, an emergent bronchoscopy was performed and thick rubbery material was extracted out from the left main bronchus. The patient received a 5-day course of oral oseltamivir and intravenous methylprednisolone for 5 days. Antibiotics (cefotaxime, netilmycin, clindamycin,and roxithromycin) and oral leukotriene modulator were administered. Massive chest physiotherapy with inhaled corticosteroids, bronchodilator, and mucolytics was carried out. In spite of the bronchoscopic removal and medical treatment, the patient experienced respiratory distress again on day 2 of hospitalization. Flexible bronchoscopy at the bedside in the intensive care unit revealed a gelatinous yellow plug in the left bronchus. Thus, a second bronchoscopic removal of bronchial casts was performed on day 3 of hospitalization (Fig. 3). After removal of the cast, dyspnea resolved and chest radiography revealed a marked improvement. On histologic examination, the firm and rubbery cast was composed of fibrinous clot with eosinophil-dominant inflammatory exudates (Fig. 4). There were no Charcot-Leyden crystals, which are frequently seen in sputum from patients with bronchial asthma. The patient was extubated on day 4 of hospitalization and discharged after 2 weeks without any complications. The patient also underwent allergic evaluations. Total IgE was 3,560 IU/mL. Some specific IgE reactions using UniCAP® (Pharmacia, Uppsala, Sweden) were positive: Dermatophagoides pteronyssi of 3.01 k/U, D. farinae of 15.9 kU/L, and Alternaria tenuis of 29.6 k/U. Unicap of cat fur, ragweed, mugwort, and Aspergillus fumigatus were negative. Eosinophil cationic protein was 12.1 ng/mL. After tachypnea was improved, spirometry was performed. The forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and FEV₁/FVC ratio, were 1.19 L, 1.20 L, and 0.99 respectively. The forced expiratory flow 25%-75% was 1.38 L/s. The serial spirometry was within normal limit on follow-up visits after discharge. A methacholine provocation test was performed 3 months later after discharge in our out-patient clinic. The provocative concentration that resulted in a 20% fall in FEV₁ was 8.0 mg/mL, which means bronchial hyperresponsiveness. Therefore, we recommended that the patient use inhaled corticosteroids for 3 months and get vaccinated for H1N1 and seasonal influenzas during influenza season. The patient has been in a good condition without respiratory infection, asthma attack, and recurrence of plastic bronchitis for 12 months since discharge.