Allergic Fungal Sinusitis

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AFS: Pathophysiology - Fungal Fiesta Fright

  • Nature: Allergic reaction to extramucosal fungi; non-invasive.
  • Hypersensitivity:
    • Predominantly Type I (IgE-mediated) against fungal antigens.
    • Possible Type III (immune complex) involvement.
  • Causative Fungi: Primarily dematiaceous molds (e.g., Bipolaris, Curvularia, Alternaria).
  • Host Factor: Atopic individuals (history of allergy, asthma).
  • Key Pathological Features:
    • Allergic Mucin: Thick, eosinophilic, "peanut butter-like" consistency.
      • Contains fungal hyphae (no tissue invasion), numerous eosinophils, Charcot-Leyden crystals.
    • Chronic inflammation causes sinus expansion. Allergic Fungal Sinusitis: CT, microscopy, gross

⭐ AFS is a non-invasive fungal sinusitis driven by a Type I hypersensitivity reaction to extramucosal fungi, not tissue invasion.

AFS: Clinical Features - Sinus Siege Symptoms

  • Chronic Sinusitis Symptoms:
    • Nasal blockage, persistent congestion.
    • Thick, discolored discharge (often unilateral).
    • Facial pain/pressure, headache.
    • ↓ Sense of smell (hyposmia/anosmia).
  • Nasal Polyposis: Frequently seen, can be extensive.
  • Allergic Mucin: Hallmark finding!
    • Thick, tenacious, "peanut butter" or "machine grease" consistency.
    • Greenish-black to brown.
  • History of atopy (asthma, eczema, allergic rhinitis). Allergic Fungal Sinusitis: CT, histology, gross

⭐ Key presentation: chronic rhinosinusitis, nasal polyposis, and thick, tenacious, 'peanut butter-like' eosinophilic mucin.

AFS: Diagnosis - Spotting Spores Sleuth

  • Nasal Endoscopy:
    • Reveals thick, tenacious, eosinophilic mucin (classic "peanut butter" or "machine oil" appearance).
  • Imaging:
    • CT Scan (PNS):
      • Sinus opacification.
      • Central hyperattenuation (pathognomonic).
      • Bony erosion/remodeling (no frank invasion). CT scan: Allergic Fungal Sinusitis
    • MRI:
      • T1: Hypointense.
      • T2: Markedly hypointense (signal void).
  • Histopathology (HPE) of Mucin:
    • Allergic mucin: Abundant eosinophils, Charcot-Leyden crystals.
    • Fungal hyphae (non-invasive); positive fungal stain.
  • Allergy Testing:
    • ↑ Total IgE & fungal-specific IgE.
    • Positive skin prick test to fungal allergens.
  • Bent & Kuhn Diagnostic Criteria (Key):
    1. Type I hypersensitivity (skin test or serology).
    2. Nasal polyposis.
    3. Characteristic CT findings.
    4. Eosinophilic mucin with fungal hyphae (no tissue invasion).
    5. Positive fungal stain or culture of sinus contents.

⭐ CT scans distinctively show central hyperattenuation in opacified sinuses; histopathology reveals allergic mucin with fungal hyphae and Charcot-Leyden crystals without tissue invasion. Bent and Kuhn criteria are key for diagnosis.

AFS: Management - Fungus Fight Formula

⭐ Management cornerstone: surgical debridement (FESS) followed by long-term corticosteroids (systemic/topical); role of antifungals is debated.

  • Goals: Eradicate fungus, ↓ inflammation, ventilate sinuses, prevent recurrence.
  • Surgical: FESS (Functional Endoscopic Sinus Surgery)
    • Essential: Remove all allergic mucin & thick fungal debris.
    • Aim: Patent sinuses for drainage & topical drug delivery.
  • Medical (Post-FESS):
    • Corticosteroids: Mainstay.
      • Systemic (Oral Prednisolone): Initial (e.g., 0.5-1 mg/kg/day), slow taper over weeks/months.
      • Topical (Nasal sprays): Long-term daily use for maintenance & recurrence prevention.
    • Nasal Saline Irrigation: Daily, high-volume; clears secretions.
    • Adjunctive Therapies (Consider):
      • Antifungals: Controversial. Systemic (e.g., Itraconazole) not routine. Topical may be an option.
      • Immunotherapy (allergen-specific): For atopy, may ↓ recurrence.
  • Follow-up: Regular endoscopic surveillance crucial for recurrence.

Endoscopic Sinus Surgery Procedure

High‑Yield Points - ⚡ Biggest Takeaways

  • AFS is a Type I hypersensitivity reaction to fungal antigens in immunocompetent, often atopic individuals.
  • Characterized by nasal polyposis and allergic mucin (thick, tenacious, eosinophilic, with fungal hyphae).
  • Allergic mucin contains Charcot-Leyden crystals and numerous eosinophils; fungi are non-invasive.
  • CT scans typically reveal hyperattenuation (hyperdensity) within affected sinuses; bony erosion can occur.
  • Diagnosis is guided by the Bent and Kuhn criteria.
  • Management primarily involves surgical debridement (FESS) followed by corticosteroids (systemic and topical).
  • Recurrence is common, necessitating long-term follow-up and management strategies for optimal outcomes.

Practice Questions: Allergic Fungal Sinusitis

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Antral lavage is used to confirm the diagnosis of _____ maxillary sinusitis and also therapeutic to remove pus.

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Antral lavage is used to confirm the diagnosis of _____ maxillary sinusitis and also therapeutic to remove pus.

chronic

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