Two distinct patient populations are seen [9]: one group of patients is patients with diabetes, especially with diabetic ketoacidosis and second group with neutropenia. Up to 80 % of invasive fungal infections in the first group are caused by fungi belonging to the order Zygomycetes such as Rhizopus sp., Rhizomucor sp., Absidia sp., and Mucor sp. [10]. This disease is more rapidly progressive with high mortality and morbidity probably due to the high virulence of these fungi as well as due to diagnosis of the disease at a late stage [9].

The other group is immunocompromised patients with severe neutropenia, e.g., patients with hematologic malignancies; patients undergoing chemotherapy or systemic steroid therapy or bone, organ, or stem cell transplantation; or patients with AIDS. Aspergillus species is responsible for up to 80 % of infections in this group [10]. In India, A. flavus [11] is the most common (80 %) while in the Middle East, A. fumigatus [12] is the most common (50 %) causative agent. Nasal septal ulceration has also been described with Fusarium species and Pseudallescheria boydii.

Among the zygomycotic species causing IFS, Rhizopus arrhizus is the most frequent agent followed by Rhizopus microsporus, Absidia corymbifera, Rhizomucor pusillus, and Mucor circinelloides [13, 14]. Another agent, Apophysomyces elegans, is also responsible for zygomycosis in India [1]. Sridhara et al. [15] have reported an increasing trend of mucormycosis in immunocompetent individuals. Three out of eight immunocompetent cases reported by them were infected by Apophysomyces elegans [15].

Wueppenhorst et al. [16] have reported a case of fulminant invasive fungal sinusitis caused by Conidiobolus incongruus in Germany. They concluded that diagnostics relying exclusively on histopathological findings could misdiagnose entomophthoramycosis as mucormycosis, and therefore, species identification is indispensable for collection of data for the adequate treatment of the condition.

Aspergillus species, dematiaceous molds such as Bipolaris, Curvularia, and Pseudallescheria boydii are the fungi implicated in this disease. Aspergillus fumigatus is the most commonly isolated fungus [17] although Mucor sp. is also known to be a causative agent especially in diabetics.

Aspergillus flavus is the fungus most often implicated in this disease. Paranasal granuloma is a peculiar syndrome associated with proptosis that has also been called indolent fungal sinusitis in immune competent persons. The fungus A. flavus shows exuberant growth with regional tissue invasion, non-caseating granulomas, giant cells, and plasma cells. This condition is known to occur in Saudi Arabia, Sudan, India, and Pakistan [11, 18]. This is rarely seen in the USA [19].

Specimen – Tissue samples or aspirates are recommended as opposed to swabs as the material obtained in tissue and aspirate is much more than in swabs, thus increasing the yield.