Allergic fungal sinusitis (AFS) is a subtype of eosinophilic chronic rhinosinusitis (CRS) characterized by type I hypersensitivity, nasal polyposis, characteristic computed tomography scan findings, eosinophilic mucus, and the presence of fungus on surgical specimens without evidence of tissue invasion. This refractory subtype of CRS is of the great interest in the pediatric population, given the relatively early age of onset and the difficulty in managing AFS through commercially available medical regimens. Almost universally, a diagnosis of AFS requires operative intervention. Postoperative adjuvant medical therapy is a mainstay in the treatment paradigm of pediatric AFS.
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Allergic fungal sinusitis (AFS) is a distinct subtype of eosinophilic CRS marked by type I hypersensitivity (by history, skin tests, or serology), nasal polyposis, characteristic computed tomography findings, eosinophilic mucus, and the presence of fungal elements of the tissue removed during surgery without evidence of fungal tissue invasion.
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AFS is most common among adolescents and young adults.
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The treatment of AFS is both medical and surgical.
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Functional endoscopic sinus surgery is the intervention of choice in this patient population, as nearly all cases of AFS will require some form of surgical management.
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Active postoperative care is crucial to the successful management of these patients, and can reduce the need for further surgical procedures.
Two videos accompany this article: One video demonstrates AFS nasal poly removal and the other demonstrates FESS for AFS at http://www.oto.theclinics.com/. Chronic rhinosinusitis (CRS) is a complex, heterogeneous disease process that affects nearly 37 million people in the United States each year and accounts for approximately $6 billion in direct and indirect health care costs. Estimates indicate that sinusitis is more widespread than arthritis or hypertension, and its effects on quality of life are comparable to that of many chronic debilitating diseases. Despite its substantial impact on quality of life and financial burden to the health care system, little is known about the etiology and pathophysiology. Moreover, controversy regarding appropriate treatment options remains. This lack of consensus pertains to the adult population but also extends into the pediatric realm, leaving a significant deficit in the understanding of pediatric sinonasal disease.
Pediatric rhinosinusitis remains one of the most common diseases of childhood. Upper respiratory tract infections represent the most significant predisposing factor, with children averaging 6 to 8 infections annually. Of these infections, 0.5% to 5% progress to acute rhinosinusitis with an unknown percentage progressing to CRS. Recent estimates indicate that patients diagnosed with CRS account for nearly 6 million pediatrician visits annually, with a substantial proportion of these being referred to subspecialty practitioners.
Classification of CRS
Rhinosinusitis is a group of disorders characterized by concurrent inflammatory and infectious processes that affect the nasal passages and the contiguous paranasal sinuses. Traditionally, symptom duration has dictated the rhinosinusitis classification schema as follows: acute (>4 weeks), subacute (4–12 weeks), and chronic (more than 12 weeks, with or without acute exacerbations).
Acute rhinosinusitis may be further subdivided by symptom pattern into:
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Acute bacterial rhinosinusitis, characterized by symptoms lasting 10 or more days beyond the onset of upper respiratory symptoms or symptomatic worsening within 10 days after initial improvement, termed double-worsening
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Acute viral rhinosinusitis.
When there are 4 or more episodes of acute bacterial rhinosinusitis per year without persistent intervening symptoms, the term recurrent acute rhinosinusitis is applied. Despite the ease and clinical applicability of the temporal scheme, classifications intended to guide clinical research have been described and include:
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Infectious etiology
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Complications
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Inflammatory markers
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Radiographic findings
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Endoscopic findings.
These systems of increased complexity allow for further patient subclassification and comparison of treatment modalities, which is of particular importance in the CRS population.
Clinical Diagnosis of Chronic Rhinosinusitis
CRS, as previously defined, is an inflammatory condition of the nasal passages and paranasal sinuses lasting 12 weeks or longer. This heterogeneous and multifactorial disease process is clinically characterized by purulent drainage, polyps, and polypoid mucosa consistent with inflammation. Although nasal endoscopy is recommended and may reveal mucosal abnormalities of the middle meatus or sphenoethmoid recess, visual confirmation of these findings is not a required criterion. The diagnosis remains clinical, owing to the multitude of health care professionals caring for these patients. The clinical diagnosis in children is often more challenging, with radiographic studies reserved for those being considered for surgery, rather than for diagnostic purposes. In children, recurrent cough is a consistent sign and symptom of rhinosinusitis, and there is evidence to suggest that rhinosinusitis is an independent risk factor for the development of recurrent cough with wheezing. Moreover, the diagnosis of CRS is rarely made in isolation and common comorbidities may include asthma, allergy, dental disease, polyposis, cystic fibrosis, and immunodeficiency syndromes.
Detailed Classification of Chronic Rhinosinusitis
The heterogeneity of CRS has made classification challenging, and numerous schemes have been developed to further divide patients into more detailed groups.
One such scheme proposed by Meltzer divided rhinosinusitis into 4 categories :
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Acute presumed bacterial rhinosinusitis
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CRS without polyps
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CRS with polyps
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Classic allergic fungal rhinosinusitis (AFS).
An alternative classification scheme proposed by Chan and Kuhn (F.A. Kuhn FA, MD, Savannah, GA, personal communication, 2009) divides CRS into 2 large categories based on the type of inflammatory response.
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Noneosinophilic chronic rhinosinusitis (NECRS)
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Eosinophilic chronic rhinosinusitis (ECRS).
NECRS is marked by neutrophilic inflammation and T-helper (Th)-1 cell predominance. Pathologic subtypes of this designation include:
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Mechanical obstruction
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Chronic bacterial sinusitis without mucin or tissue eosinophilia
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Cystic fibrosis
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Primary ciliary dyskinesia
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Noneosinophilic rhinosinusitis with nasal polyps.
The latter example has recently been described by Borish, who reported that noneosinophilic polyps tend to display more profound glandular hypertrophy, fibrosis, and mononuclear and mast cell infiltrates than eosinophilic counterparts.
ECRS is marked by eosinophilic inflammation in the setting of Th-2 and interleukin-5 predominance, and is extremely difficult to control. It is hypothesized that some external trigger activates and upregulates these pathways in the setting of a genetic predisposition toward the characteristic eosinophilic response. Pathologic subtypes of ECRS include:
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Aspirin-sensitive asthma with nasal polyps
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AFS
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AFS without fungus
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Staphylococcus aureus– induced superantigen rhinosinusitis
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Chronic gram-negative rhinosinusitis with nasal polyps
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Eosinophilic CRS of unknown etiology.
Fungal sinusitis
There are 4 distinct types of fungal sinusitis with varying clinical presentations and physical examination findings:
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Acute fulminant invasive fungal sinusitis
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Chronic indolent invasive fungal sinusitis
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Mycetoma or fungus ball sinusitis
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AFS.
Invasive sinusitis is often a life-threatening condition that uniformly requires surgical debridement and aggressive antifungal therapy. The subtypes are distinguished from each other based on the course of onset and the populations affected.
Acute fulminant invasive fungal sinusitis is a life-threatening condition that is rapidly progressive and affects immunocompromised patients.
Chronic indolent invasive fungal sinusitis generally affects the immunocompetent population, and is marked by fungal invasion into the sinonasal mucosa.
Mycetoma or fungus ball sinusitis is characterized by noninvasive, fungal proliferation and expansion within a sinus in a nonatopic, immunocompetent patient, and can be definitively treated by debridement.
AFS represents the final type of allergic sinusitis and is the topic of the remainder of this discussion.
Fungal sinusitis
There are 4 distinct types of fungal sinusitis with varying clinical presentations and physical examination findings:
- 1.
Acute fulminant invasive fungal sinusitis
- 2.
Chronic indolent invasive fungal sinusitis
- 3.
Mycetoma or fungus ball sinusitis
- 4.
AFS.
Invasive sinusitis is often a life-threatening condition that uniformly requires surgical debridement and aggressive antifungal therapy. The subtypes are distinguished from each other based on the course of onset and the populations affected.
Acute fulminant invasive fungal sinusitis is a life-threatening condition that is rapidly progressive and affects immunocompromised patients.
Chronic indolent invasive fungal sinusitis generally affects the immunocompetent population, and is marked by fungal invasion into the sinonasal mucosa.
Mycetoma or fungus ball sinusitis is characterized by noninvasive, fungal proliferation and expansion within a sinus in a nonatopic, immunocompetent patient, and can be definitively treated by debridement.
AFS represents the final type of allergic sinusitis and is the topic of the remainder of this discussion.
Allergic fungal sinusitis
AFS is a distinct subtype of eosinophilic CRS marked by :
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Type I hypersensitivity (by history, skin tests, or serology)
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Nasal polyposis
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Characteristic computed tomography findings ( Fig. 1 )
Fig. 1
Coronal and sagittal noncontrasted computed tomography maxillofacial scans from a pediatric patient with documented allergic fungal sinusitis. There is opacification of the bilateral paranasal sinuses with characteristic bony expansion and erosion.
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Eosinophilic mucus ( Fig. 2 )
Fig. 2
Endonasal endoscopic view of allergic mucin within the paranasal sinuses of a pediatric patient with documented allergic fungal sinusitis.
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Presence of fungal elements of the tissue removed during surgery without evidence of fungal tissue invasion ( Fig. 3 ).
