Old Liu went to the doctor for a few months because of a cough, and the local hospital took a film saying he had pneumonia, so he came to our hospital after a month of infusion but no improvement. When we looked at the lung CT, we saw a large hypodense shadow in both lower lungs, but the patient only had cough and shortness of breath after activity, but no fever symptoms. What was even more strange was that the patient’s blood count had a mild to moderate increase in white blood cells, and the percentage of monocytes was significantly higher. The patient was then examined by bronchoscopy, and no secretions were seen in the lumen, so alveolar lavage was performed, and the result was pure saline, but the liquid came out as milk, and the pathological examination confirmed alveolar protein deposition. Due to the abnormal blood picture, Liu went to the hematology department to check the chronic monocytic leukemia, so Liu has a very rare disease, chronic monocytic leukemia combined with alveolar protein deposition, the author’s work for more than ten years is the first case. Because of the large area of the old Liu lesion, so the city a respiratory doctors gave him a general anesthesia in the operating room after the whole lung lavage, with more than a dozen liters of saline down, finally basically his lungs to clean, old Liu also feel smooth gas people are also more comfortable. How do you get alveolar protein deposition? Why can wash out so much “milk” from the lungs? It turns out that the most basic unit of the lung is the alveoli, two lungs have millions of alveoli, these alveoli usually maintain an open state, so that the outside world oxygen through all levels of bronchi to the alveoli and then into the capillaries to supply the whole body. The substance that can keep the alveoli in such a state is called alveolar surface active substance, which is secreted by the alveolar epithelial cells. As we all know, we have to metabolize every day, and this surface active substance will lose its function after a long time to be removed by the macrophages in the alveoli. The problem is that the macrophages become dysfunctional and are unable to remove these substances, and then a terrible consequence arises. However, there is a very specific presentation of this disease on imaging that helps us to identify it, and that is the resemblance on CT to the stone roads we have in the park, which we call the paving stone sign. How can this disease be treated? The main and proven most effective way is to perform alveolar lavage to clean out this useless garbage and restore the alveoli to function again.