Differential Diagnosis for Sudden Loss of Sense of Smell

Single Most Likely Diagnosis

• Post-viral olfactory dysfunction: This is the most common cause of sudden loss of sense of smell, often occurring after a viral upper respiratory infection. The condition can be persistent, lasting for a year or more.

Other Likely Diagnoses

• Chronic rhinosinusitis: Inflammation and infection of the nasal passages and sinuses can lead to a decrease in the sense of smell. This condition is common and can cause persistent symptoms.
• Nasal polyps: Growths in the nasal passages can obstruct the flow of air and reduce the sense of smell.
• Head trauma: Injury to the head can damage the olfactory nerves, leading to a loss of sense of smell.
• Medication side effects: Certain medications, such as antibiotics and antihistamines, can cause a decrease in the sense of smell as a side effect.

Do Not Miss Diagnoses

• Tumors (e.g., olfactory neuroblastoma, meningioma): Although rare, tumors in the nasal cavity or brain can cause a loss of sense of smell. Missing these diagnoses can have serious consequences, including delayed treatment and poor outcomes.
• Neurodegenerative diseases (e.g., Parkinson's disease, Alzheimer's disease): Certain neurodegenerative diseases can cause a loss of sense of smell, and early diagnosis is crucial for management and treatment.

Rare Diagnoses

• Kallmann syndrome: A genetic disorder characterized by a loss of sense of smell and delayed puberty.
• Congenital anosmia: A rare condition where a person is born without a sense of smell.
• Toxic exposure: Exposure to certain toxins, such as heavy metals or chemicals, can cause a loss of sense of smell.
• Autoimmune disorders (e.g., multiple sclerosis, lupus): Certain autoimmune disorders can cause a loss of sense of smell, although this is a rare symptom.