Diagnosing aPAP

Autoimmune pulmonary alveolar proteinosis (aPAP) is often misdiagnosed because its symptoms mimic more common respiratory conditions like pneumonia, bronchitis, and asthma. Because aPAP is so rare, many doctors may have never diagnosed or treated it before, which can delay an accurate diagnosis, on average, by 18 months.

Misdiagnoses may continue until failure to respond to therapy prompts reconsideration and further diagnostic testing. When patients are misdiagnosed, they are at risk of inappropriate treatment and poorer outcomes.

Since many pulmonologists are not familiar with testing for aPAP specifically, they may suggest invasive tests that could require hospitalization, such as bronchoscopy or a lung biopsy. These tests can disrupt a patient’s daily activities, thereby negatively impacting their quality of life.

On a computerized tomography (CT) scan, aPAP appears as ground-glass opacification with a "crazy paving" pattern – a nonspecific sign with a wide etiology, including infection, pulmonary edema, chronic interstitial disease, and acute alveolar injuries. A clinical history of slowly progressive dyspnea, with or without cough and fatigue, together with the characteristic high-resolution CT findings, should prompt the consideration of aPAP.