Fungal Sinusits

• A combination of type 1 and 3 hypersensitivity reaction is thought to be involved in the pathogenesis of Allergic fungal sinusitis. 
• It  is thought to involve direct stimulation of eosinophils by a subset of helper T cells (TH2) primed by fungal antigens.
• It results in vigorous inflammation and polyp formation.
• Causative organisms includes  usually those of the Dematiaceae family, but Aspergillus species are also seen.
• Patients usually presents with features of chronic sinusitis.
• The diagnostic criteria for allergic fungal sinusitis (AFS) are the presence of characteristic allergic mucin, type I hypersensitivity (eosinophilic-lymphocytic inflammation), absence of fungal invasion, immuno-compromised individuals and radiological confirmation (areas of high attenuation on CT scan).
• Patients are treated with systemic steroids, surgery, and nasal irrigations.

  Topical Steroids are indicated post-surgery. 

SINUS MYCETOMA/BALL

• This condition is usually unilateral and involves the maxillary sinus.
• Mucopurulent, cheesy, or claylike material is present at the time of surgery.
• Patients with sinusitis mycetoma are immunocompetent.
• Allergic conditions and fungus-specific IgE are less common.

INVASIVE FUNGAL SINUSITIS

• Invasive fungal sinusitis includes the acute fulminant type, which has a high mortality rate if not recognized early and treated aggressively, and the chronic and granulomatous type

ACUTE INVASIVE FUNGAL SINUSITIS– MUCORMYCOSIS

• Caused by – rhizopus, rhizomucor, cunninghamella.
• The higher prevalence of mucormycosis in India turned out to be statistically significant  in comparison with all other countries
  

Predisposing factors:

• Organ transplant recipients
• Long term desferroxamine therapy
• Immunosuppression due to steroids or cytotoxic drugs
• Hematological malignancy
• Diabetis Mellitus
• Chronic renal failure

Five forms of mucormycosis are:

• Rhinocerebral (most common site)
• Pulmonary mucormycosis (2nd most common)
• Cutaneous
• Gastrointestinal
• Disseminated
• Miscellaneous

Clinical Presentation

• Intitially, the disease runs a subtle course with only fever and rhinorrhea. Later on, it invades the orbit and intracranial cavity with rapid loss of vision, meningitis, cavernous sinus thrombosis and multiple cranial nerve palsies.
• It has marked predilection for vascular invasion leading to widespread thrombosis, tissue necrosis, and gangrene.
• Characteristic nasal finding is a dark necrotic turbinate surrounded by pale mucosa blackish discharge and crusts.
• M/C site is middle turbinate followed by middle meatus and septum.
• Investigation of choice is MRI, while biopsy is confirmatory.
• Diagnosis: Biopsy with histopathologic examination is the most sensitive and specific modality for definitive diagnosis. Biopsy shows wide, thick walled, ribbon like, aseptate hyphal elements that branch at acute angles.
• Histologic examination of affected tissue reveals either infarction, with invasion of blood vessels by many fungal hyphae, or acute necrosis, with limited inflammation and hyphae.
• Treatment: Includes IV amphotericin-B, heparin, hyperbaric oxygen, and  surgical debridement.

CHRONIC INVASIVE FUNGAL SINUSITIS

• It is a slowly progressive fungal infection with a low-grade invasive process and usually occurs in patients with diabetes.
• Orbital apex syndrome, which is characterized by a decrease in vision and ocular immobility due to a mass in the superior portion of the orbit, is usually associated with this condition.
• Aspergillus fumigatus is the only fungus associated with chronic invasive fungal sinusitis.
• On microscopy,shows hyaline, narrow, septate and  irregular branching hyphae with invasion of the blood vessels .. 

GRANULOMATOUS INVASIVE FUNGAL SINUSITIS

• This condition has been reported almost exclusively in immunocompetent individuals from North Africa.
• Generally, proptosis is associated with granulomatous invasive fungal sinusitis.
• Aspergillus flavus exclusively has been associated with granulomatous invasive fungal sinusitis.

Exam Question

• The diagnostic criteria for allergic fungal sinusitis (AFS) are the presence of characteristic allergic mucin, type I hypersensitivity (eosinophilic-lymphocytic inflammation), absence of fungal invasion, immuno-compromised individuals and radiological confirmation (areas of high attenuation on CT scan).
• Type 1 and Type 3 Allergic reaction is seen in patients with Allergic fungal sinusitis.
• Causative organism in a diabetic with orbital cellulitis and maxillary sinusitis showing hyaline, narrow, septate and irregular branching hyphae with invasion of the blood vessels  on microscopy would be Aspergillus.
• Mucormycosis  has a predilection for vascular invasion.
• Orbital mucormycosis may occur as  a complication of Diabetic Ketoacidosis.
• Amphoterecin B IV is used for invasive fungal sinusitis.