A Rare Case of Pulmonary Alveolar Proteinosis Superimposed by Severe COVID-19 Pneumonia: Case Report.

COVID-19 pneumonia is a strong radiological mimicker of pulmonary alveolar proteinosis (PAP), making their differentiation difficult. PAP is a rare diffuse lung disease caused by the accumulation of surfactant lipoproteins within the alveoli, resulting in impaired gas exchange and respiratory failure, with an estimated prevalence of 3.7-6.2 cases per million. This report presents a rare case of PAP complicated by COVID-19 pneumonia in a 42-year-old man who presented with chills, fatigue, dyspnea and fever. Clinical, laboratory and radiological features were thoroughly assessed. High-resolution CT revealed a crazy-paving pattern with patchy consolidations, diffuse ground-glass opacities and septal thickening. Early recognition of lung diseases with overlapping imaging features is essential to guide management and prevent adverse outcomes. The coexistence of PAP and COVID-19 was associated with rapid clinical deterioration and poor prognosis. Further studies are needed to clarify underlying mechanisms and optimise treatment strategies.