We present the case of a 43-year-old woman with a diagnosis of pulmonary alveolar proteinosis, on chronic treatment with sargramostim, a recombinant granulocyte-macrophage colony-stimulating factor, who presented with the nephrotic syndrome secondary to biopsy-proven membranous nephropathy. We discuss potential underlying mechanisms, including speculated effects of sargramostim on mesangial cells and the kidney resident macrophages, and review the existing literature on the potential association between these two disorders.