Costello syndrome (CS) is a rare disease with intellectual disability, characterized by failure to thrive, short stature, joint laxity, loose soft skin, and distinctive facial features. This disease is caused by heterozygous germline mutations in the HRAS proto-oncogene. Cardiac and neurological abnormalities are the most common. Cardiovascular manifestations include valvular pulmonary stenosis, arrhythmia and hypertrophic cardiomyopathy. Neurological manifestations are dominated by hydrocephalus, seizures, and tethered spinal cord. Respiratory system manifestations have been reported in people with CS, but a full description of the different lung involvement and respiratory symptoms in these patients is not available. We report the case of a 19-year-old non-smoking man, followed for a Costello syndrome since the age of 8 months, who complained of exertional dyspnea and chest pain for over 18 months. The chest CT scan showed bullous emphysema of the left lung with a giant bulla in the left upper lobe measured than 20 cm long axis responsible for passive atelectasis. Pulmonary function tests revealed a severe non-reversible obstructive ventilatory defect. Faced with the worsening of his dyspnea despite treatment with bronchodilators and recurrent respiratory infections, it was decided to surgically remove the the giant emphysematous bulla. After bullectomy, a clinical and functional respiratory improvement was noted.