Pulmonary Alveolar Proteinosis:a Case Report And Literature Review

BackgroundPulmonary alveolar proteinosis(PAP) is a rare disease caused by accumulation of surfactant components in the alveoli and terminal airways. Gas exchange impairment and ventilation dysfunction gradually bring about progressive dyspnea. Chest HRCT scan shows typical "crazy paving" appearance, while broncho alveolar lavage reveals PAS positive "milky " fluid. Broncho alveolar lavage is the standard therapy, and is effective in most patients. However, immune-modulatory therapy, such as GM-CSF supplemental therapy, Rituximab and plasmapheresis are also effective in many patients. As a rare disease, there might be some misdiagnosis and missed diagnosis due to limited clinical knowledge.A brief introduction of the caseA 48-year-old male patient chiefly complained to suffer from fever and productive cough for more than 20 days. More than 20 days ago, the patient had a fever without obvious incentive, his body temperature can be up to 38.0℃. Being accompanied by cough and white phlegm, the patient had no dyspnea, hemoptysis, night sweats or other symptoms other than the medical history described above. With chest radiograph showing diffuse alveolar opacities, he was considered as "pulmonary infection" at other hospital and received anti-infection therapy for several weeks. Fever was finally controlled, nevertheless, productive cough and radiological findings didn’t relieve. Then he was admitted to our hospital, the physical examination revealed dry rales in right lung, while high-resolution CT-scan showed typical "crazy paving" pattern. Pulmonary function tests indicated diffusion capacity dysfunction, and the arterial blood gas analysis revealed hypoxemia. Laboratory examinations showed no evidence of virus, tuberculosis or any atypical pathogens infection, and the autoantibody spectrum is basically normal.The serum levels of CEA, CA15-3 and CYFRA21-1 are elevated. In order to clarify the diagnosis, bronchoscopy, broncho alveolar lavage, and trans-bronchial right lung biopsy were implemented further. The BAL fluid had a muddy appearance, with hyaline material found positive on PAS staining, and its etiological examination was normal. The histopathology of right lung tissue revealed PAS staining positive material within alveolar spaces. Last but not least, careful cytological examination of both sputum, BAI fluid and lung tissue indicated no cancer cells. Combining all the results above, we diagnosed this patient with PAP. After given three times of broncho alveolar lavage treatment, his symptoms and signs significantly relieved, CT-scan showed a decrease in the presence of "crazy-paving" pattern. In the past one year, he came back several times for follow-up visits. A distinct relieve of radiological findings suggest that lung lavage treatment was effective and the disease progressed slowly.Conclusions1.The manifestations of PAP are not specific, compatible symptoms and signs combined with remarkable imaging abnormalities are typical for these patients. Such discrepancy should lead to the consideration of PAP in the differential diagnosis, especially when antibiotics and glucocorticoid treatments are not effective.2.Typical findings in histopathology of the lung tissue and cytological analysis of BALF, such as patchy PAS positive material within alveolar spaces,are vital to diagnosis.3.Whole lung lavage or broncho alveolar lavage is the standard therapy,and is effective in most PAP patients.