PSMA6 and chronic obstructive pulmonary disease: COPD is a condition with progressive, nonreversible airflow limitation and pathological changes in the lung, among other mechanisms, due to alterations in the immune response; although the known pathological changes are mainly due to damage from tobacco smoking, biomass-burning smoke exposure and, less frequently, alpha-1 anti-trypsin deficiency, despite smoking cessation, the disease progression is not entirely understood.