Conidiobolus

Conidiobolus is a genus of fungi in the order Entomophthorales, within the phylum Entomophthoromycota (historically placed in Zygomycota). It comprises several species that are commonly found in soil and decaying plant matter, where many are saprotrophic. Some species are entomopathogenic, and a minority can cause infections in humans and other animals, a condition known as conidiobolomycosis.

Morphology and life cycle: Conidiobolus species typically produce coenocytic hyphae and proliferate asexual conidia on specialized conidiophores; the conidia are generally globose to subglobose and can be abundant in culture. Sexual reproduction yields thick-walled zygospores in some species. The organisms favor warm, moist environments and can persist in the soil or on plant debris.

Clinical relevance: The best-known human pathogen is Conidiobolus coronatus, which can cause rhinofacial conidiobolomycosis. Infections are most often reported in tropical and subtropical regions and may occur after inhalation of conidia or following trauma. Clinical presentations include chronic, painless swelling of the nasal and facial regions, sometimes with tissue ulceration and bone involvement. Diagnosis relies on tissue histology and culture, showing large, sparse-septate hyphae with characteristic conidia; molecular methods may assist in species identification.

Treatment and prognosis: Management typically involves prolonged antifungal therapy, with agents such as itraconazole or voriconazole being used in many cases; amphotericin B has variable efficacy. Surgical debridement may be required for extensive disease. Early diagnosis and appropriate therapy improve outcomes, though prognosis depends on the site and extent of infection. Conidiobolus infections are rare but are considered important in the differential diagnosis of subcutaneous and facial fungal infections in at-risk regions.