Pulmonary Alveolar Proteinosis Due to Chronic Cotton Dust Exposure and Hepatitis C Infection

Abstract

INTRODUCTION: Pulmonary alveolar proteinosis (PAP) is an orphan lung disease due to the deposition of surfactant in the alveoli. Secondary causes of PAP include hematological malignancies, immunodeficiency, chronic exposure to organic and inorganic dust. Hepatitis C association with PAP has been a controversy. We report a case of PAP with significant cotton dust exposure with Hepatitis C infection. CASE PRESENTATION: A 56 year old male cotton mill worker presented with cough, breathlessness since 4 months. He was treated for pulmonary tuberculosis 2 years back. He was in respiratory distress. Computed tomography of chest showed bilateral upper lobe fibrosis and crazy pavement appearance in middle and lower lobes bilaterally. Serum hepatitis C antibodies were positive. Bonchoalveolar lavage was positive for periodic acid Schiff stain. Whole lung lavage was done using a double lumen endotracheal tube. Milky white fluid was drained. Patient was started on Granulocyte Monocyte Colony Stimulating Factor (GMCSF). Patient improved clinically and radiologically. DISCUSSION: Signaling defect of GMCSF curtails the terminal differentiation of alveolar macrophages and their capacity to degrade the surfactant material, hence leading to PAP. Cotton contains cellulose, which is not catabolized by humans due to the lack of enzymes breaking it down. Hence the inhaled cellulose is engulfed by the macrophages in the alveoli causing overburdening of the macrophages, diminishing the surfactant catabolism. Hepatitis C virus earlier known to be only hepatotropic, is now known to affect monocytes and macrophages; leading to dysfunction of macrophages in precipitating PAP. CONCLUSION(S): Cotton dust, Hepatitis C, mycobacterium tuberculosis all present in our patient are known to be associated with macrophage impairment. We speculate that all the three factors acted together in precipitating PAP rather than being just a chance association. Hence it is vital to evaluate a patient with PAP, for analyzing the additional trigger factors apart from the occupational exposure, not only for the etiological aspect but also from the management perspective.