Laboratory Studies
Unfortunately, findings from laboratory studies are nonspecific for zygomycosis.[7, 10] Diagnosis requires a high index of suspicion, a host with appropriate risk factors, and evidence of tissue invasion with the characteristic appearance of broad nonseptate hyphae with right-angle branches. No serologic tests are available, and blood cultures are of no benefit.[1]
- Rhinocerebral zygomycosis
- Discharge scrapings may be examined with potassium hydroxide (KOH) to reveal broad irregularly shaped hyphae with right-angle branching (as seen in the image below).
Material from the periorbital tissue of a woman with poorly controlled diabetes mellitus with facial and periorbital swelling due to zygomycosis is stained with periodic acid-Schiff stain (X 560). The material demonstrates the classic appearance of irregularly shaped broad hyphae with right-angle branching (arrow). - Fungal stains of biopsy material obtained from affected tissue remains the mainstay for a definitive diagnosis.
- Fungal culture of biopsy tissue also may be helpful, but results frequently are negative despite positive histopathology. In fact, fungal culture results are only positive in 15-25% of cases.
- Discharge scrapings may be examined with potassium hydroxide (KOH) to reveal broad irregularly shaped hyphae with right-angle branching (as seen in the image below).
- Pulmonary zygomycosis
- Sputum smear and cultures are rarely helpful.
- Lung tissue biopsy is generally needed for diagnosis.
- Gastrointestinal zygomycosis
- Most cases of gastrointestinal zygomycosis are diagnosed at surgery or postmortem.
- Fungal stains and cultures of biopsy material are needed for definitive diagnosis.
- Cutaneous zygomycosis: Diagnosis of this type requires fungal stains and cultures of a skin biopsy.
- Disseminated zygomycosis
- Blood cultures are of no benefit.
- Fungal stains and cultures of affected tissue and histopathologic identification of the fungus are needed.
- Brain biopsy may be helpful.
- Cerebrospinal fluid analysis is generally nonspecific, even in the presence of brain involvement.
- Cerebrospinal fluid abnormalities include slightly increased pressure, modest pleocytosis with predominant polymorphonuclear cells, and slightly elevated protein levels. Hypoglycorrhachia is unusual. Erythrocytosis is occasionally observed. Fungal stains and culture results are rarely positive.
Imaging Studies
- Rhinocerebral zygomycosis
- Plain radiographs of sinuses and orbits may demonstrate sinus mucosal thickening, with or without air-fluid levels, but this is nonspecific.
- CT scans with contrast or MRI may demonstrate erosion or destruction of bone or sinuses and delineate the extent of disease (as seen in the image below).
A CT scan of the head of a patient with zygomycosis shows involvement of the paranasal sinuses and periorbital soft tissues.
- Pulmonary zygomycosis
- Chest radiographs may demonstrate single or multiple large masslike infiltrates, pulmonary nodules, and cavitary lesions. These lesions, however, are indistinguishable from those caused by aspergillosis.
- CT scan with contrast may help delineate the extent of disease.
- Gastrointestinal zygomycosis
- Abdominal radiographs may demonstrate air under the diaphragm in patients with perforation.
- Barium studies of the upper GI tract or colon may demonstrate a filling defect or a masslike effect that suggests zygomycosis.
- Disseminated zygomycosis
- CT scan of the chest and head may demonstrate invasive disease and delineate the extent of disease.
- CT scan of the abdomen and pelvis may demonstrate lesions in the liver, spleen, kidney, pancreas, stomach, and omentum.
Procedures
- Bronchoscopy with bronchoalveolar lavage and transbronchial biopsy provides adequate tissue to diagnose pulmonary zygomycosis.
- CT-guided percutaneous lung biopsy may also be beneficial.[12]
- Open lung biopsy may be required if bronchoscopy findings are negative.
- Endoscopy provides direct examination of the esophagus and stomach, the most commonly affected organs in patients with gastrointestinal zygomycosis.
- Brain biopsy may be required to establish a diagnosis.
Histologic Findings
Fixed tissue can be stained with hematoxylin and eosin (H&E). Fungal hyphae may be demonstrated with Grocott methenamine-silver stain or periodic acid-Schiff (PAS) staining. The typical appearance demonstrates the fungus as broad, nonseptate hyphae with acute right-angle branching.
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