1 Introduction
With routine prenatal ultrasound scans performed, more and more congenital cystic lesions of the lung are diagnosed in infants[1], but the incidence is rare, which is present in 1 per 10,000–35,000 births[2]. The differential diagnosis of congenital cystic lesions contains congenital cystic adenomatoid malformation (CCAM), pulmonary sequestration (PS), bronchogenic cyst, congenital lobar emphysema (CLE), and persistent pulmonary interstitial emphysema (PPIE) and so on.
Pulmonary interstitial emphysema (PIE) is a rare cystic disease of infants. PIE is an air leak syndrome, characterized by gas dissecting pulmonary interstitium, along the bronchovascular bundles. There are three clinical types of PIE, including acute IPE, local persistent PIE (LPPIE) and diffuse persistent PIE (DPPIE) [3, 4]. Acute IPE is lesser than seven days in duration, diffuse persistent PIE is observed when small cysts are noted in all lobes of the lung, while local persistent PIE affected only one lobe [5]. Chest computed tomography (CT) scan sometimes was limited to diagnose PIE. Sometimes, CT showed cystic lung lesions mimicking CCAM in the postnatal period[6]. The definitive diagnosis is histological. A histological diagnosis of PIE was established through the wall of cysts composed of a thin layer of discontinuous fibrous tissue and lined with uninucleated or/and multinucleated macrophages[7, 8].
PIE frequently occurs in premature infants with positive pressure mechanical ventilation[9, 10]. However, it has also been reported rarely in both nonventilated infants and full-term infants[11, 12]. Pursnani et al.[12] showed a 3-month-old infant with LPPIE who had no history of respiratory distress syndrome (RDS) and mechanical ventilation, the patient had a medical history of viral pneumonia 1 month prior to surgery, indicating respiratory infection may be associated with PPIE.
However, there were just a few reports of PPIE with respiratory infection[11-19], and possible infectious pathogens were still unclear. With the development of molecular methods of identification, the metagenomic next-generation sequencing (mNGS) is a novel, rapid, simple, and convenient approach in the clinical identification of infectious diseases.
In present study, we reported six rare cases of PPIE with respiratory infection, followed by successfully surgical lobectomy. To our best knowledge, it is the first time to detect the possible infectious pathogens in PPIE by using mNGS.