Nasal polyposis is an inflammatory condition of unknown etiology. Nasal polyps are the most common tumors of the nasal cavity. Approximately 30% of patients with nasal polyps test positive for environmental allergies. The prevalence of nasal polyps is increased in children with cystic fibrosis and persons with known aspirin hypersensitivity. Nasal polyposis can impair a person's quality of life more than perennial allergic rhinitis. Olfaction and nasal obstruction are the most important considerations in terms of symptoms.
Nasal polyposis results from chronic inflammation of the nasal and sinus mucous membranes. Chronic inflammation causes a reactive hyperplasia of the intranasal mucosal membrane, which results in the formation of polyps. The precise mechanism of polyp formation is incompletely understood.
In 1990, Tos reported 10 pathogenic theories of nasal polyp formation: 
Adenoma and fibroma theories
Necrosing ethmoiditis theory
Glandular cyst theory
Mucosal exudate theory
Cystic dilatation of the excretory duct and vessel obstruction theory
Periphlebitis and perilymphangitis theory
Glandular hyperplasia theory
Gland new formation theory
Ion transport theory
Multiple chemical mediators have been identified in nasal polyps but their significance has not been completely elucidated. Some of these mediators may be released by the polyps themselves and others by the eosinophils found in certain subsets of polyps. Cysteinyl leukotriene receptors and interleukin-5 (IL-5) appear to be the most well studied.
Nasal polyps are present in 5% of nonallergic people and only 1.5% of people with allergic rhinitis. No racial or sexual predilection is reported. The prevalence is increased in patients with cystic fibrosis and aspirin-hypersensitivity triad.
Morbidity from polyps is directly related to their location and size.
Obstruction of the sinus ostia frequently occurs and may lead to acute or chronic sinus conditions. With increased growth, polyps can cause bony destruction because they can exert pressure on bone. Polyps may cause destruction of the nasal bones or other facial bones.
Nasal obstruction due to polyposis can also lead to hyposmia or even anosmia.
Nasal polyps are not known to be premalignant. However, they may be confused with papillomas, including inverting papillomas, which are known to be precursors of malignant lesions. In addition, polyps can sometimes arise from inflammation caused by malignant or premalignant nasal lesions. These polyps can obstruct visualization of the more concerning lesions and sometimes cause delay in diagnosis.
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