[A case of bronchiolitis obliterans secondary to human metapneumovirus bronchiolitis]

Human metapneumovirus (hMPV), formerly classified in Paramyxoviridae family is now moved into Pneumoviridae, which was described as a novel family. It causes upper and lower respiratory tract infections (LRTIs) usually in children younger than five years old. The recent epidemiological studies indicated that hMPV is the second most frequently detected virus in LRTIs of young children, following the respiratory syncytial virus (RSV). Bronchiolitis obliterans (BO) is a chronic obstructive lung disease characterized by fibrosis of the distal respiratory airways. It is usually a result of an inflammatory process triggered by a LRTI related to adenovirus, RSV, Mycoplasma pneumoniae, measles virus, Legionella pneumophila, influenza virus or Bordetella pertussis as a causative agent. In this report, a case of hMPV bronchiolitis complicated with BO has been reported to point out the complications and severity of the clinical progress belongs to this virus. A three-month-old female patient has admitted to our pediatric intensive care unit with the diagnosis of acute bronchiolitis and respiratory failure. She was born at term, weighing 2950 gram and had been hospitalized in newborn intensive care unit for 11 days with the diagnosis of transient tachypnea of the newborn and neonatal sepsis. On auscultation, there were bilateral crepitant rales, wheezing and prolonged expirium. Her oxygen saturation was 97-98% while respiratory support was given with a non-rebreathing reservoir mask. Complete blood count, procalcitonin and C-reactive protein levels were in normal ranges. The chest radiography yielded right middle lobe atalectasia, left paracardiac infiltration and bilateral air trapping. A nasopharyngeal swab sample was analyzed by a commercial multiplex real-time reverse transcriptase-polymerase chain reaction (Thermo Fisher Scientific®, USA) developed for the detection of 15 respiratory viruses. Her sample yielded positive result for only hMPV. On the 4th day of hospitalization, the patient was intubated because of respiratory failure and carbon dioxide retention. She was extubated on the 19th day but could not tolerate. In the thorax computed tomography (CT), bilateral hyperinflation, patchy infiltration, mosaic perfusion and atelectasis especially bilateral posterior areas were detected. Bronchoscopy was normal except mild bronchomalacia in right middle lobe bronchus. The patient was diagnosed as BO secondary to hMPV bronchiolitis, according to the clinical, virological, bronchoscopic and thorax CT results. On the 76th day of admission, she was discharged with respiratory support with home ventilation via a tracheostomy cannula and medical treatments of oral metilprednisolone, nebulized salbutamol and budesonide. In conclusion, hMPV should not be undervalued especially in infants with severe LRTI that can be complicated with BO.