RESUMEN
Membranous glomerulonephritis is one of the most common causes of nephrotic syndrome in adults. Pulmonary alveolar proteinosis (PAP) is a rare lung disease in which abnormal accumulation of surfactant occurs within the alveoli. We describe a 61-year-old man with concurrent membranous glomerulonephritis and PAP, which is very rare; both are pathophysiologically related to an abnormal immune response. A patient came to hospital with leg edema but no respiratory symptoms. Chest X-ray and CT showed classical PAP findings, which are ground-glass opacities with interlobular septal thickening, in both lung fields. A bubbly whitish secretion retrieved via broncho-alveolar lavage showed neutrophils and lymphocytes as well as Periodic acid-Schiff-positive proteinaceous materials. A kidney biopsy revealed findings of membranous glomerulonephritis with irregular subepithelial deposits by electron microscopy. At 1 year after diagnosis, the membranous glomerulonephritis was well under control with steroids and mycophenolate mofetil but PAP became aggravated gradually and whole-lung lavage was needed.