Croup is usually cause by infection with viral laryngotracheobronchitis. It causes a hoarse voice, barking cough and a high-pitched wheeze on inhalation.
Hypersensitivity pneumonitis and extrinsic allergic alveolitis are respiratory disorders involving inflammation of the airways or alveoli of the lungs.
Bronchiectasis is a lung disease. Inflammation of the bronchi and bronchioles leads to permanent dilation. Mucus accumulates, causing chronic infection.