Phenotypic Features of Cystic Lung Disease in Proteus Syndrome: A Clinical Trial.

Rationale: Limited information is available regarding cystic lung disease in Proteus syndrome, a rare overgrowth disorder caused by a somatic activating variant in AKT1 . Objectives: To define the phenotype of cystic lung disease in Proteus syndrome. Methods: Medical records, pulmonary function tests, and chest computed tomography of 39 individuals with Proteus syndrome evaluated at a single center were retrospectively reviewed. Lung histopathology from five affected individuals was examined. Results: Cystic lung disease affected 26 (67%) of 39 individuals. The mean age of affected individuals was 17.1 years. The lung cysts varied in size and location. Focal regions of heterogeneous lung parenchyma resembling emphysema were found in 81% of affected individuals. Mass effect was seen in 12% of affected individuals; pneumothorax occurred in one. Dyspnea and respiratory infections were reported by 38% and 35% of affected individuals, respectively. Abnormal pulmonary function and scoliosis were found in 96% of affected individuals. Lung disease progressed in seven of 10 affected individuals, and all five affected individuals younger than 20 years of age had progressive cystic lung disease. Three affected individuals had symptomatic improvement after lung resection. Histopathology showed cystic air space enlargement of varying severity. Conclusions: Cystic lung disease is common in Proteus syndrome and is likely to progress in affected individuals younger than 20 years of age. Screening asymptomatic individuals with Proteus syndrome for cystic lung disease is indicated. Surgical lung resection is a therapeutic option for affected individuals with severe disease. Clinical trial registered with www.clinicaltrials.gov (NCT00001403).