Abstract
BACKGROUND Hunter syndrome is a multisystem metabolic inherited disease belonging to the large group of mucopolysaccharidoses (MPSs). Hunter syndrome is also known as MPS type II. Its association with respiratory symptoms has been well documented in the literature; however, it is uncommon that these patients initially present with diffuse lung disease and respiratory failure. Diffuse lung disease has a wide range of differential diagnoses that can overlap in some clinical and radiological aspects, making physicians struggle to quickly reach a final diagnosis. CASE REPORT We report a case of a full-term male infant who presented postnatally with progressive respiratory distress, hypoxemia, and radiologically-demonstrated ground-glass opacity and pneumothorax requiring mechanical ventilation and an extensive workup including CT scan of the chest, a flexible and rigid bronchoscopic examination of the airway with bronchoalveolar lavage, and whole-exome sequencing, which eventually resulted in a diagnosis of Hunter syndrome. After enzyme therapy was initiated, the patient showed marked improvement in clinical status and biological and imaging data and was weaned off oxygen a few months later. CONCLUSIONS The diagnostic approach for patients with diffuse lung disease is challenging and requires centers with expertise to reach a final diagnosis, especially in the presence of an unusual clinical presentation. The choice of the diagnostic approach can be influenced by factors such as the patient's critical condition, clinical presentation, imaging data, genetic analysis, and family decision.