Polyps occur in 36% of patients with aspirin intolerance and 7% of patients with asthma. They are more common in patients who are not allergic with an incidence of 13% in non-allergic asthma and 5% of atopic asthma. In patients with rhino-sinusitis 2% have polyps with 5% occurring in non-allergic rhinitis and 1.5% in allergic rhinitis. In childhood asthma/rhinitis there is very low incidence of 0.1%. There is an increased incidence of inflammatory polyps in patients with cystic fibrosis.
- Most Polyps arise in the middle meatus and Ethmoid region
- Respiratory tract epithelium lines the sinuses and this consists of pseudostratified ciliated columnar epithelium with goblet cells
- Areas of metaplastic squamous cell epithelium can occur on the polyp surface.
Four histological types
- Oedematous, Eosinophilic 90%
Oedematous stroma, hyperplasia of goblet cells
Numerous mast cells and eosinophils
Thickened hyalinized basement membrane
Pronounced Inflammatory infiltrate predominantly T cells
- Chronic Inflammatory Polyp - No Goblet cell hyperplasia
- Polyp with hyperplasia of Seromucinous glands - abundance of glands and ductal structures
- Polyp with Stromal Atypia can be mistaken for neoplasm
There is no clear cause of polyps but a number of factors have been implicated (Box1)
The anatomy of the ethmoid labrynth
Lack of sinus vascularity
Eosinophils and mast cells
Large numbers of eosinophil and mast cells are found throughout the polyp. There is also increased numbers of Mast Cells in the adjacent inferior turbinate. These cells contribute to the increased levels of mediators which in turn gives rise to the chronic symptoms
Early stages of polyp formation
- Epithelial damage, necrosis and rupture due to tissue pressure
- Prolapse of the lamina propria caused by inflammatory oedema
- Epithelialization of the prolapse
- Gland formation
- Elongation and enlargement of the glands due to gravity
- Changes of the epithelium and stroma of polyp
- CT in the Coronal plane is preferred in this view the Osteomeatal canals are clearly shown
- CT should be performed after medical therapy
- Patients unable to tolerate prone positioning can have axial imaging with coronal reconstructions
- "Hanging Head" technique can be used
Clinical relationship of nasal polyps to asthma
In patients with polyps the incidence varies depending on the study. From as low as 4% of patients with polyps having asthma to as high as 40% with most studies showing approximately 33%. The estimates of aspirin intolerance in nasal polyps also vary from 4-26%
Nasal polyps and IgE - polyps in allergic people
Although Nasal polyps are more common in patients without allergy. If patients with nasal polyps are allergic then they are more likely to have recurrence of the polyps.
Nasal polyps and aspirin
There are a number of studies showing that aspirin desensitisation in patients with aspirin sensitivity can cause regression of the polyps. Individuals with aspirin sensitivity should be referred to a specialist in allergy for assessment for desensitisation to aspirin.
In patients with nasal polyps and aspirin intolerance there is an increased rate of recurrence and the interval between polypectomies is reduced. Individuals with aspirin sensitivity should be referred to a specialist in allergy for assessment for desensitisation to aspirin.
Allergic fungal sinusitis/polyposis
There is an increased incidence of nasal polyps associated with allergic fungal sinusitis.
In this condition the fungus is acting as an allergen in an immunocompetent person.
There is eosinophilia in some patients with this condition.
Topical nasal steroids
In Double Blind Placebo Controlled Studies 400 - 800 mcg Budesonide over 8 weeks has shown efficacy.
In a follow-up Open trial only 33% of patients needed surgery over the next 12 months.
Short course steroids have shown equal effectiveness to polypectomy via snare.
Preoperative steroids are often given in severe disease to facilitate surgery.
A number of studies have shown that leukotriene anatagonists can reduce symptoms in patients with nasal polyps.
Respiratory tract epithelium lines the sinuses and this consists of psuedostratified ciliated columnar epithelium with goblet cells.
Areas of metaplastic squamous cell epithelium can occur on the polyp surface.
© ASCIA 2010
The Australasian Society of Clinical Immunology and Allergy (ASCIA) is the peak professional body of Clinical Immunologists and Allergists in Australia and New Zealand.
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ASCIA Education Resources (AER) information is reviewed by ASCIA members and represents the available published literature at the time of review. Information contained in this document is not intended to replace professional medical advice and any questions regarding a medical diagnosis or treatment should be directed to a medical practitioner.
Content updated January 2010