Zygomycosis

Zygomycosis in humans is caused by Rhizopus, Mucor, and Rhizomucor while Cunninghamella, Absidia, Saksenaea, and Apophysomyces are genera that are less often associated [1]. It typically affects immunocompromised individuals or those with diabetes mellitus and can manifest in five major forms: rhinocerebral, pulmonary, abdominopelvic and gastric (gastrointestinal), primary cutaneous, and disseminated [2] [3] [4] [5].

• Rhinocerebral zygomycosis is the commonest form encountered in clinical practice and involves the nose, followed by the paranasal sinuses, eyes, and brain. It manifests as nasal congestion, epistaxis, headache, fever, unilateral facial or orbital swelling, visual disturbances, and lesions with black eschar on the palate or nose.
• Pulmonary zygomycosis occurs in patients with a hematological malignancy, or in those with severe neutropenia, organ transplant recipients, and following high-dose steroid therapy. Clinically it presents with fever, cough, dyspnea, and chest pain.
• Cutaneous zygomycosis presents with blisters or ulcers with eschar, and pain with inflammation around a wound. It can occur primarily following local trauma or inoculation or secondarily due to hematogenous dissemination of the fungi.
• Abdominopelvic and gastrointestinal (GI) zygomycosis accounts for only 10% of all zygomycosis infections [1]. It is caused by ingestion of the fungus resulting in necrotic ulcerations, and ischemic gangrene of the stomach and colon. It has an extremely high mortality rate as it is associated with a high incidence of bowel perforation and is difficult to diagnose [6]. Symptoms include nausea, vomiting, abdominal pain and GI bleeding in malnourished individuals, infants with low birth weight, and chronic renal failure patients on peritoneal dialysis.
• Disseminated zygomycosis typically occurs in seriously ill patients with several comorbid medical conditions making it difficult to pinpoint symptoms due to zygomycosis. Patients present with a history of headaches, fever, visual disturbances, and altered sensorium progressing to coma. The infection can start in the lungs and then spread to the central nervous system, heart or abdominal organs causing ischemic infarction.

Diagnosis of zygomycosis depends on a high index of suspicion, especially in immunocompromised patients, along with the identification of the characteristic broad aseptate fungus with its right angle branching pattern in tissue samples obtained from necrotic areas [3] [4]. Special stains like Grocott's methenamine silver stain or periodic acid-Schiff (PAS) are necessary to demonstrate the fungal hyphae. Laboratory tests, blood culture, and serology tests do not help in the diagnosis [5] [7] [8].

Rhinocerebral zygomycosis

Physical examination may reveal periorbital cellulitis, proptosis, and ophthalmoplegia and black necrotic eschar on the hard palate or nasal mucosa. Plain sinus radiographs are non-specific and may show only mucosal thickening, with or without air-fluid levels. Computed tomography (CT) scans with contrast and magnetic resonance imaging (MRI) of the sinuses, orbit and brain are required to delineate the extent of the disease.

Pulmonary zygomycosis

Pleuritic rub and rhonchi can be detected on examination. Sputum smear and culture are not helpful but diagnosis can be confirmed with bronchoscopic bronchoalveolar lavage and transbronchial biopsy. If bronchoscopy findings are unclear, then open lung biopsy may be required. Radiographs of the chest demonstrate mass-like or nodular or cavitary lesions indistinguishable from lesions caused by aspergillosis. CT scan with contrast can provide information about the extent of disease while CT guided lung biopsy can provide tissue for histology [9].

GI zygomycosis

Decreased bowel sounds, guarding or rebound tenderness, and localized-to-diffuse abdominal tenderness may be present. Upper GI endoscopy helps to detect zygomycosis in the esophagus and stomach but a majority of cases are diagnosed during surgery or postmortem with a tissue biopsy. Plain radiographs of the abdomen may demonstrate air under the diaphragm in patients with perforation and barium studies of the upper GI tract or colon may show filling defects suggestive of zygomycosis. Abdominopelvic CT scan could demonstrate lesions within the intraabdominal organs and the omentum.

Cutaneous zygomycosis

Solitary lesions initially indurated and erythematous progressing to necrotic ulceration are seen. A biopsy sample from the lesion helps to diagnose the condition.

Disseminated zygomycosis

Sudden onset focal neurologic deficits, lethargy, altered sensorium, coma, with necrotic ulcerations on the skin or oral cavity, are found. As the cerebrospinal fluid analysis is nonspecific, a brain biopsy is the mainstay of diagnosis. CT scan of the chest and head may demonstrate invasive disease and delineate the extent of disease.

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