Differential Diagnoses for Sinusitis

Primary Differential Diagnoses

The American Academy of Allergy and Clinical Immunology suggests that allergic rhinitis typically presents with clear nasal discharge, nasal itching, sneezing, seasonal pattern, and response to antihistamines, distinguishing it from bacterial sinusitis which features purulent discharge and facial pain 3
Eosinophilic nonallergic rhinitis should be considered in patients with chronic nasal symptoms without evidence of allergy or infection, according to the Journal of Allergy and Clinical Immunology 1, 2
Vasomotor rhinitis presents with nasal symptoms triggered by environmental factors without allergic or infectious etiology, as noted by the Journal of Allergy and Clinical Immunology 1, 2
Vascular headaches and migraines are important differentials, as headache attributed to chronic sinusitis could actually be a migraine equivalent, as suggested by the Journal of Allergy and Clinical Immunology 1, 2

Acute bacterial sinusitis should be suspected when upper respiratory tract infection symptoms persist beyond 10-14 days, or when symptoms worsen after initial improvement within 10 days, according to the Journal of Allergy and Clinical Immunology 1, 2, 3
Persistent symptoms, such as purulent rhinorrhea, postnasal drainage, and facial pain, correlate with increased likelihood of bacterial disease, as noted by the Journal of Allergy and Clinical Immunology 1, 2
The American Academy of Otolaryngology-Head and Neck Surgery recommends assessing for severe presentation, including high fever and purulent nasal discharge for 3+ consecutive days 3

Nasal polyps and other anatomic variants can cause chronic obstruction mimicking infectious sinusitis, according to the Journal of Allergy and Clinical Immunology 1, 2
Deviated nasal septum and other anatomic abnormalities should be assessed in recurrent cases, as suggested by the American Academy of Otolaryngology-Head and Neck Surgery 4

Fungal ball presents with chronic unilateral symptoms, typically in maxillary or sphenoid sinuses, with dense accumulations of hyphae but no eosinophilic mucin, as noted by the Journal of Allergy and Clinical Immunology 2
Allergic fungal sinusitis involves eosinophilic mucin and should be distinguished histologically from fungal ball, according to the Journal of Allergy and Clinical Immunology 2
Invasive fungal sinusitis occurs in immunocompromised patients and presents with fever, headache, epistaxis, mental status changes, and insensate nasal ulcers, requiring aggressive debridement and systemic antifungal therapy, as suggested by the Journal of Allergy and Clinical Immunology 1, 2

The American Academy of Allergy and Clinical Immunology recommends assessing for environmental exposures, genetic predisposition, allergic rhinitis, rhinitis medicamentosa, cystic fibrosis, ciliary dyskinesia, cocaine abuse, and immunodeficiency in patients with recurrent acute rhinosinusitis or chronic rhinosinusitis 1, 4
Asthma should also be assessed, as suggested by the American Academy of Otolaryngology-Head and Neck Surgery 4

Not all mucosal thickening on imaging represents active sinusitis, and imaging findings must be correlated with clinical symptoms, as noted by Praxis Medical Insights 5
Failure to recognize migraine as the cause of "sinus headache" leads to inappropriate treatment, according to the Journal of Allergy and Clinical Immunology 1, 2

Patients should return immediately for orbital complications or neurological complications, such as eye pain, swelling, visual changes, periorbital edema, severe headache, altered mental status, or neck stiffness, as suggested by Praxis Medical Insights 3