Zygomycosis


Zygomycosis

Description, Causes and Risk Factors:

A broad term that includes mucormycosis and entamophthoramycosis; usually applied when culture is not available and the clinical entity is unclear.

Zygomycosis is the broadest term to refer to infections caused by bread mold fungi of the zygomycota phylum. However, because zygomycota has been identified as polyphyletic, and is not included in modern fungal classification systems, the diseases that Zygomycosis can refer to are better called by their specific names: mucormycosis (after Mucorales), phycomycosis (after Phycomycetes) and basidiobolomycosis (after Basidiobolus). These rare yet serious and potentially life-threatening fungal infections, usually affect the face or oropharyngeal (nose/mouth) cavity. Zygomycosis type infections are most often caused by common fungi found in soil and decaying vegetation. While most individuals are exposed to the fungi on a regular basis, those with immune disorders (immunocompromised) are more prone to fungal infection. These types of infections are also common after natural disasters, such as tornadoes or earthquakes, where people have open wounds that have become filled with soil or vegetative matter.

The pathogens that cause zygomycosis are commonly found in the environment on fruit, on bread, and in soil and are common components of decaying organic debris. These organisms are ubiquitous and generally saprophytic, rarely causing disease in immunocompetent hosts, but they are the third-most-common cause of invasive fungal infection in immunocompromised patients, especially stem cell transplant recipients and patients with underlying hematologic malignancies.

Fungi are ubiquitous in the natural world, often found in association with plants, mammals, and insects. Accordingly, humans are continually exposed to multiple genera of fungi via various routes, including the respiratory and gastrointestinal routes, which allow the possibility of colonization. Depending on the interaction between host mucosal defense mechanisms and fungal virulence factors, colonization may be transient or persistent, or local disease may ensue.

Zygomycosis due to entomophthoraceous fungi is caused by species of two genera, Basidiobolus and Conidiobolus. Infections are chronic, slowly progressive and generally restricted to the subcutaneous tissue in otherwise healthy individuals. Other characteristics that separate these infections from those caused by mucoraceous fungi are a lack of vascular invasion or infarction and the production of a prolific chronic inflammatory response, often with eosinophils and Splendore-Hoeppli phenomena around the hyphae.

Zygomycosis caused by B. ranarum is a chronic inflammatory or granulomatous disease generally restricted to the subcutaneous tissue of the limbs, chest, back or buttocks, primarily occurring in children and with a predominance in males. Initially, lesions appear as subcutaneous nodules which develop into massive, firm, indurated, painless swellings which are freely movable over the underlying muscle, but are attached to the skin which may become hyperpigmented but not ulcerated.

Zygomycosis caused by Conidiobolus sp. is a chronic inflammatory or granulomatous disease that is typically restricted to the nasal submucosa and characterised by polyps or palpable restricted subcutaneous masses. Clinical variants, including pulmonary and systemic infections have also been described. Human infections occur mainly in adults with a predominance in males (80% of cases). Most cases have been reported from the tropical rain forest areas of central and west and south and central America. Infections usually begin with unilateral involvement of the nasal mucosa. Symptoms include nasal obstruction, drainage and sinus pain. Subcutaneous nodules develop in the nasal and perinasal regions and progressive generalised facial swelling may occur. Infections also occur in horses usually producing extensive nasal polyps and other animals. Conidiobolus coronatus is also a recognised pathogen of termites, other insects and spiders.

Predisposing factors include uncontrolled diabetes mellitus or acidosis, steroid induced hyperglycemia, especially in patients with leukemia and lymphoma, renal transplant and concomitant treatment with corticosteroids. Infections usually begin in the paranasal sinuses following the inhalation of sporangiospores and may involve the orbit, palate, face, nose or brain.

Symptoms:

Zygomycosis>

Fever.

  • Pus draining from nose.

  • Stuffy or runny nose.

  • Nosebleeds.

  • Fatigue.

  • Impaired vision.

  • Bulging eyes.

  • Ulcer in roof of mouth.

  • Infection of tissue around nose.

  • Convulsions.

  • Blood clots.

  • Inflammation of cranial nerves.

  • Progressive pneumonia.

  • Gastrointestinal tract infection.

  • Kidney infection.

  • Skin infection.

  • Coughing and vomiting blood.

  • Abdominal pain.

  • Flank pain.

  • Hardened patch of skin around infected area.

  • Altered mental status.

  • Diagnosis:

    Direct Microscopy: (a) Scrapings, sputum and exudates should be examined using 10% KOH & Parker ink or Calcofluor mounts; and (b) Tissue sections should be stained with H&E (Hematoxylin and eosin stain) and GMS (Gomori methenamine-silver stain). Examine specimens for broad, infrequently septate, thin-walled hyphae, which often show focal bulbous dilations and irregular branching.

    There are currently no commercially available serological procedures for the diagnosis of zygomycosis. Although some laboratories have developed ELISA (enzyme-linked immunosorbent assay) tests for the detection of antibodies to Zygomycetes.

    Treatment:

    Take aggressive surgical measures to d

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