Merciful anosmia is seen in
Merciful anosmia is seen in atrophic rhinitis(Ozaena). There is foul smell from the nose, but the patient himself is unaware of smell due to marked anosmia due to degenerative changes Ref: Dhingra 7e pg 173.
Nasal polyp
Atrophic rhinitis
Rhinosporidiosis
Rhinoscleroma
Nose and paranasal sinuses