Cystic fibrosis. Light micrograph of a section through a bronchus (airway) of the lungs in a case of cystic fibrosis (mucoviscidosis). The bronchus is clogged with mucus, causing the severe breathlessness seen in this inheritable condition. Over-production of mucus and chronic inflammation of the lungs is treated with physiotherapy and antibiotic drugs, but the condition progresses and is ultimately fatal. Magnification unknown.