Rhinofacial conidiobolomycosis (entomophthoramycosis)
Introduction
Conidiobolomycosis is a subcutaneous mycosis caused by Conidiobolus coronatus. It is characterized by rhinofacial edema and infiltration, usually affecting immunocompetent hosts. The characteristic histopathologic finding is the “Splendore-Hoeppli phenomenon,” which is an antigen–antibody reaction manifested by hyphae surrounded by an eosinophilic halo. An etiological diagnosis is established by culture, but the fungus is rarely isolated.
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Historical data
The first case of phycomycosis due to Entomophthora coronata was reported in 1961 in a horse from Texas. In 1964, the fungus was named Conidiobolus coronatus, and this condition was called “entomophthoramycosis conidiobolae.”1 In 1965, the first human cases were reported simultaneously in Jamaica and the Congo.2, 3 In 1968, it was called “rhinoentomophthoromycosis.” Currently, we prefer the name conidiobolomycosis rather than entomophthoramycosis.
Epidemiology
Conidiobolomycosis is an uncommon infection. It occurs in tropical areas, mainly in northeastern Brazil, Central America, the Caribbean Islands, India, and Africa. Isolated cases have been reported in the United States and Australia, with approximately 120 cases reported worldwide. It is predominately found in immunocompetent male farmers who have been exposed to the fungus.
Etiopathogenesis
The causative agent is C coronatus, class Zygomycetes, order Entomophthorales, family Ancylistaceae.1 This fungus has been isolated from soil and rotting plant matter.4 It infects mites and aphids, such as Allium schoenoprasum,5 and animals such as chimpanzees, llamas, sheep, horses, and frogs.6, 7, 8, 9 Infection likely occurs by traumatic implantation or by inhalation. The fungus produces various enzymes, such as elastases, esterases, collagenases, and lipases, which are involved in the
Clinical features
Conidiobolomycosis has an unknown incubation period. It is a rhinofacial zygomycosis, characterized by subcutaneous inflammation of the submucosa in the central facial region. Infection begins with a nasal nodule that grows slowly over time. Nasal obstruction occurs first, followed by a diffuse erythematous infiltration with thickening of the skin on the nose. Later, an important increase in volume and a deformity of the central facial structures is observed (Fig. 1, Fig. 2, Fig. 3). Affected
Mycologic examination
Lesions of conidiobolomycosis rarely show exudates, but direct examination with potassium hydroxide can be performed in tissue fragments or specimens from bronchial lavage.15 Findings include short, thick hyphae (4-10 μm in diameter) with absent or few septa.1, 16 Cultures are performed in Sabouraud dextrose agar, without cycloheximide or chloramphenicol, at 30° to 37°C. Colonies are fast growing (4 days) and are white, beige, or brown, glabrous and folded, have a floury and grainy look,
Histopathologic data
In our experience, the biopsy specimen must be taken from the glabella. The fungal structures are easily identified with hematoxylin and eosin, periodic acid–Schiff (PAS) or Gomori-Grocott stain (Figure 6).4 Biopsy specimens show a suppurative granuloma with lymphocytes, histiocytes, multinucleated giant cells, plasma cells, and eosinophils. Nonseptated hyphae surrounded by an eosinophilic halo are occasionally visualized (Splendore-Hoeppli phenomenon).
Laboratory data
Leukocytosis, eosinophilia, and an increased erythrocyte sedimentation rate can be found.1 The C coronatus C-6 antigen–antibody reference system is considered specific for identification of this fungus. Horses infected with C coronatus that were successfully treated presented a reduction or absence of precipitins. Results of immunodiffusion tests should be interpreted carefully because they may be confused with Basidiobolus spp and Pythium insidiosum.20, 21 Immunodiffusion tests of culture
Differential diagnosis
The differential diagnosis of conidiobolomycosis includes sarcoidosis, rhinosporidiosis, and benign and malignant tumors of the nasal cavity such as nasal polyps, lymphoma, scleroma, and sarcoma.1, 4
Complications
The main complications are nasal obstruction and dysphagia. Death can occur in untreated patients or in those with immunosuppression mainly due to diabetes mellitus or prolonged use of corticosteroids.
Treatment
Anecdotal reports describe patients being treated with amphotericin B (0.5 mg/d) for 2 weeks or 1 month, dapsone, (1-2 mg/kg of body weight daily), and ketoconazole (400 mg/d), itraconazole (300 mg/d), or fluconazole (300 mg/d) for 6 months. Other treatments include potassium iodide, 5-fluocitosyne, trimethoprim/sulfamethoxazole, and terbinafine. In our experience, the best results are achieved with itraconazole (300 mg/d) for at least 6 months. In many patients, treatment must be combined or
Prognosis
If treatment is early and adequate, the prognosis is good, and mortality is uncommon (2%). There is no consensus about the duration of treatment, but it must be continued for long periods—even years—until a negative mycologic examination and a good clinical response is achieved. Deformities are difficult to resolve. As in other subcutaneous mycoses, follow-up is performed with mycologic and clinical examination.1
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