Curschmann's crystals are seen in -
Pathology of Asthma
Gross -

Lungs are overdistended because of overinflation and there may be a small area of atelectasis.
The most striking macroscopic finding is occlusion of bronchi and bronchioles by thick tenacious mucus plugs.

Histology -

Characterized by the presence of numerous eosinophils and neutrophils.

Curschmann's spiral - Whorls of shed epithelium in mucous plugs.
Charcot -Leyden crystals - Collection of crystalloids made up of eosinophilic membrane protein.
The other characteristic histological finding of Asthma is collectively called Airway remodelling, it includes -

Thickening of the basement membrane of the bronchial epithelium.
Edema and an inflammatory infiltrate in the bronchial walls with a prominence of eosinophils and mast cells.
An increase in the size of submucosal glands.
Hypertrophy of bronchial wall muscle.

The "airway remodelling" contributes to airflow obstruction.
Bronchial asthma
Bronchiectasis
Chronic bronchitis
Wegener's granulomatosis