Causes of Rhinosinusitis
Viruses. Acute viral rhinosinusitis can be caused by over 200 different viruses. Some of the most frequent ones are rhinoviruses (25%–80%), followed by coronaviruses (10%–20%), influenza viruses (10%–15%) and adenoviruses (5%). No virus whatsoever is detected in 20%–30% of cases. The proportion may vary depending on the time of year, the population group being analysed or the detection method.
Bacteria. When the symptoms get worse after 5 days or persist for more than 10 days, this is called acute bacterial rhinosinusitis. It is a bacterial superinfection of a mucous membrane that has been affected by an acute viral infection or common cold. According to the European position paper on rhinosinusitis and nasal polyps (EPOS 2012) the bacteria most frequently isolated are Streptococcus pneumoniae, Haemophilus influenzae and Moxarella catarrhalis. Other species, such as streptococci, anaerobic bacteria and Staphylococcus aureus, are also isolated at lower percentages.
It is unclear what role microorganisms play in the development of chronic rhinosinusitis. The cultures taken from most patients reveal a polymicrobial and fungal flora.
Risk factors associated with Rhinosinusitis
Acute rhinosinusitis. The main risk factor for developing acute bacterial rhinosinusitis is changes to the mucus transport mechanism (mucociliary clearance) across the nasal epithelium. This epithelium is lined with hairs, called cilia, which form the structure responsible for mucus transport. In the case of a viral infection, the cilia may be destroyed, thus facilitating bacterial superinfection, but an abnormality in the nasal cavities could also alter the direction of mucociliary clearance and cause mucus to accumulate.
Any change associated with ciliary function results in changes to mucus transport and accumulation in the paranasal sinuses.
Chronic rhinosinusitis. There are several risk factors:
Chronic alteration to mucociliary transport. It is characterised by cough, rhinitis and chronic sinusitis due to abnormal ciliary function in the respiratory tract. It manifests in diseases such as primary ciliary dyskinesia or Kartagener’s syndrome.
Mucus with altered characteristics as occurs in cases of cystic fibrosis. In this disease, the patient’s mucus is thicker and harder to transport.
Sensitivity non-steroidal anti-inflammatories.It is a disorder of the metabolism of these drugs that can trigger a chronic inflammation of the lower and upper airway (paranasal sinuses).
Immune system disorders. Such as HIV or common variable immunodeficiency.
Allergic rhinitis or another atopic reaction that affects the paranasal sinuses. Allergic rhinitis causes swelling in the nasal mucosa that can partially block the drainage holes from the paranasal sinuses.
Environmental factors. For example, regular exposure to contaminants such as tobacco smoke.
Pregnancy. Around 20% of pregnant women suffer symptoms of nasal congestion during pregnancy. It is unknown why this occurs.
Anatomical variations. Septal deviation, alterations to the uncinate process or concha bullosa.