What is the most common type of sinusitis in adults, particularly those with a history of allergic rhinitis or asthma?

Most Common Type of Sinusitis in Adults

Acute rhinosinusitis (ARS) caused by viral upper respiratory infections is the most common type of sinusitis in adults, with approximately 20 million cases of acute bacterial rhinosinusitis (ABRS) occurring annually in the United States, making it one of the most frequently encountered conditions in clinical practice. 1

Epidemiology and Prevalence

• Twelve percent of the US adult population (nearly 1 in 8 adults) reported being diagnosed with rhinosinusitis in the prior 12 months, making it more common than hay fever (7%), bronchitis (4%), or chronic obstructive pulmonary disease (4%). 1

• Rhinosinusitis accounts for more outpatient antibiotic prescriptions than any other diagnosis, with antibiotics prescribed in approximately 82% of visits despite guidelines encouraging judicious use. 1

• Among the anatomic sites, maxillary sinusitis is the most common location for acute disease in adults. 2

Types of Sinusitis by Duration

• Acute rhinosinusitis (ARS) is defined as symptoms lasting less than 4 weeks and represents the vast majority of sinusitis cases. 1

• Most ARS begins as a viral upper respiratory infection that extends into the paranasal sinuses, which may be followed by bacterial superinfection in a subset of cases. 1

• Chronic rhinosinusitis (CRS) is defined as symptoms lasting 12 weeks or longer and accounts for 7.1% of primary care antibiotic-related visits compared to 3.9% for ARS. 1

Special Consideration: Allergic Rhinitis as a Predisposing Factor

For adults with a history of allergic rhinitis or asthma (as mentioned in your expanded question), the relationship with sinusitis is particularly important:

• Allergic rhinitis commonly precedes the development of recurrent or chronic sinusitis, with 40-84% of adults with chronic rhinosinusitis having coexisting allergic rhinitis. 1, 3

• The nasal obstruction and inflammation associated with allergic rhinitis interrupts normal mucociliary clearance and leads to retention of secretions within the sinus cavities, creating conditions favorable for bacterial infection. 1

• Patients with both allergic rhinitis and chronic rhinosinusitis demonstrate more extensive abnormalities on CT scans compared to those without allergic rhinitis (67% versus 33% abnormal scans). 1, 3

• Patients with recurrent or chronic sinusitis should be evaluated for the presence of underlying allergy, as effective treatment of allergic rhinitis may decrease sinusitis frequency. 1, 3

Common Bacterial Pathogens in ABRS

When bacterial superinfection occurs:

• Streptococcus pneumoniae and unencapsulated Haemophilus influenzae are responsible for more than 50% of cases of acute bacterial sinusitis in adults. 1

• Moraxella catarrhalis is also a common pathogen, particularly in children but also seen in adults. 1, 2