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Acute sinusitis is inflammation of the paranasal sinuses lasting less than 4 weeks, most commonly affecting the maxillary and ethmoid sinuses. It typically follows viral upper respiratory infections but can be complicated by bacterial superinfection, particularly with Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis.
Viral infections or allergens cause mucosal edema and increased mucus production, leading to obstruction of sinus ostia and impaired ciliary function. This creates an anaerobic environment that promotes bacterial overgrowth and secondary bacterial infection. The resulting inflammation and purulent discharge cause the characteristic pressure symptoms and pain.
Diagnosis is primarily clinical, focusing on symptom duration, purulent nasal discharge, facial pain/pressure, and nasal obstruction. Bacterial sinusitis is suspected when symptoms persist beyond 10 days, worsen after initial improvement, or are severe with high fever and purulent discharge. Most cases are viral and self-limiting, requiring only symptomatic treatment, while bacterial cases may warrant antibiotic therapy.