A 43-year-old non-smoker man presented to the emergency department with exertional dyspnoea and left pleuritic pain for 3 days. He denied fever or cough. He had history of pulmonary embolism, deep venous thrombosis and multiple opportunistic infections. At presentation, his oxygen saturation was 94% with venturi mask at 31% and lung auscultation showed basal crackles. He had no signs of peripheral oedema or deep venous thrombosis. Inflammatory parameters were within normal range. High-resolution chest computed tomography showed diffuse ground-glass opacities with interlobular and intralobular septal thickening — a pattern described as “crazy paving” (Panel A). Bronchoscopy yielded milky appearing lavage fluid (Panel B) and pathological testing revealed proteinaceous material positive on periodic acid–Schiff staining. These findings confirmed a diagnosis of pulmonary alveolar proteinosis (PAP). He underwent volume lavage of both lungs sequentially. At 6-month follow-up, he still maintained substantial improvement, with oxygen saturation of 94% in ambient air. PAP is a rare pulmonary disease caused by impaired surfactant turnover [1]. Although the crazy paving pattern is often associated with PAP [1], it’s not specific and can be seen in other conditions, including acute respiratory distress syndrome, pulmonary haemorrhage, organizing pneumonia, lipoid pneumonia and infections like Pneumocystis jirovecii [2] and SARS-CoV-2 pneumonia.