Utility of anti-GM-CSF antibodies in the diagnosis of pulmonary alveolar proteinosis: a case report

INTRODUCTION: Pulmonary alveolar proteinosis (PAP) is a disease characterized by the accumulation of lipoprotein-aceous material in the alveoli as a consequence of deficient processing of pulmonary surfactant. It is classified into primary, secondary, and congenital forms. Primary PAP (autoimmune origin) is characterized by the presence of antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF), while secondary PAP is due to multiple causes such as exposure to certain environmental substances. We present a case of a patient with probable mixed PAP, primary and secondary, due to exposure at the patient’s workplace. CASE PRESENTATION: A 35-year-old male patient attends the outpatient clinic of pulmonology due to symptoms of exertional dyspnea for one year. Pulmonary function tests are performed, and the chest X-ray reveals diffuse bilateral lung involvement with a ground-glass pattern. Incision and excision lung biopsy show findings compatible with predominant PAP in the left lower lobe (LLL). Additionally, a positive anti-GM-CSF antibody result is obtained. The patient is treated with bronchoalveolar lavage (BAL) and nebulized sargramostim. The patient shows satisfactory progress. DISCUSSION: The clinical, analytical, radiological, and histological manifestations were compatible with the diagnosis of autoimmune PAP, and there was suspicion of secondary PAP due to exposure to rock wool. The role of the laboratory, in this case, was essential for the diagnostic confirmation of PAP by performing the determination of anti-GM-CSF antibodies.