Differential Diagnosis for Nasal Sore with Purulent Discharge and Foul Smelling Odor

Single Most Likely Diagnosis

• Acute Bacterial Rhinosinusitis: This condition is characterized by inflammation of the nasal passages and sinuses due to a bacterial infection, often following a viral upper respiratory infection. The symptoms of purulent discharge, foul odor, and response to amoxicillin (a broad-spectrum antibiotic) align well with this diagnosis. The bacterial causes can include Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, all of which are typically sensitive to amoxicillin.

Other Likely Diagnoses

• Nasal Furuncle or Carbuncle: These are infections of the hair follicles in the nose, which can become filled with pus, causing pain, swelling, and purulent discharge. They are usually caused by Staphylococcus aureus and can respond to antibiotics like amoxicillin, although they may require drainage.
• Chronic Rhinosinusitis with Acute Exacerbation: This condition involves long-standing inflammation of the nasal passages and sinuses with a sudden worsening of symptoms, which can include purulent discharge and foul odor. While chronic rhinosinusitis may not fully resolve with antibiotics, acute exacerbations can respond to amoxicillin.

Do Not Miss Diagnoses

• Invasive Fungal Sinusitis: Although less common, this condition can present with similar symptoms and is critical to diagnose early because it can be life-threatening, especially in immunocompromised patients. It requires prompt antifungal treatment and possibly surgical intervention.
• Malignancy (e.g., Squamous Cell Carcinoma of the Nasal Cavity): While rare, nasal cavity cancers can present with symptoms like foul-smelling discharge and should be considered, especially in patients with risk factors such as smoking or exposure to certain chemicals.

Rare Diagnoses

• Granulomatosis with Polyangiitis (formerly known as Wegener's Granulomatosis): This is a rare autoimmune disorder that can affect various parts of the body, including the nasal passages and sinuses, leading to symptoms like purulent discharge and destruction of nasal tissue.
• Leprosy (Hansen's Disease): In rare cases, leprosy can affect the nasal mucosa, leading to chronic inflammation, discharge, and potentially a foul odor. This diagnosis would be considered in patients who have traveled to or lived in areas where leprosy is endemic.