Deep or systemic mycoses can be subdivided into
- Cosmopolitan deep mycoses, such as aspergillosis, candidosis and cryptococcosis. They are caused by fungi that occur worldwide.
- Exotic deep mycoses, including coccidioidomycosis and histoplasmosis and infection with Penicillium marneffei, the pathogens of which have a limited geographical distribution.
Exotic deep mycoses
The exosaprophytic moulds that cause exotic deep mycoses have the lungs as their portal of entry. They are dimorphic, i.e. they occur in two forms. In the environment they are filamentous, while in vivo they exhibit another morphology that of yeasts. These moulds are capable of causing disease in patients without predisposing factors. The severity of the condition varies according to the inoculum and the patient’s immune status. In patients without predisposing factors dissemination is rare and associated with a very large inoculum. In at risk patients (AIDS) dissemination always occurs even if only a small number of spores are inhaled. Dissemination leads to the secondary form in which numerous deep foci are possible and cutaneous lesions are also often observed.
The laboratory diagnosis is based on the specific morphology which the pathogen exhibits in vivo and on the culture of the saprophytic phase. Manipulation of the cultures is dangerous! There are reliable serological tests which are of diagnostic and prognostic value. For therapy as an alternative to amphotericin B use is increasingly, and successfully, being made of the azoles (itraconazole), particularly for the secondary chronic forms or relapse prevention (cfr. cryptococcosis).