INTRODUCTION

Dematiaceous fungi have melanin-like pigments in the cell walls and can cause a variety of infections in humans known as phaeohyphomycosis (phaeo is Greek for "dark"). The most severe of the phaeohyphomycoses are infections of the central nervous system (CNS). The nomenclature of these infections is confusing, and there are scant data on appropriate management. The mycology, clinical features, and treatment of cerebral phaeohyphomycosis will be reviewed here.

MYCOLOGY

The common factor among the dematiaceous fungi is the presence of melanin pigments in the cell walls and spores. These pigments cause the hyphae to appear golden brown when examined under the microscope, and this can sometimes suggest the diagnosis when examining clinical histopathology specimens. The fungal nomenclature of the agents of cerebral phaeohyphomycosis has undergone much change, and this has resulted in confusion about the identities of the causative fungi. The most common causes of cerebral phaeohyphomycosis, for example, are Cladosporium trichoides [1,2], Xylohypha bantiana [3-7], Cladosporium bantianum [8], and Cladophialophora bantiana [9]. It is now generally accepted that all of these fungi should be collectively known as Cladophialophora bantiana. One can assume that all of the previous reports on infections due to these seemingly different fungi were caused by the same species.

Other causative fungi include Wangiella dermatitidis (also known as Exophiala dermatitidis) [10,11], Dactylaria gallopava (also known as Ochroconis gallopava) [12,13], Fonsecaea pedrosoi [14], Bipolaris spicifera (also known as Drechslera spicifera) [15,16], Rhinocladiella mackenziei (also known as Ramichloridium mackenziei and Ramichloridium obovoideum) [17,18], and Aureobasidium species [19]. Specimens are frequently not cultured; thus, species identifications are often not made [20]. In these cases, the diagnosis of phaeohyphomycosis depends upon demonstration of pigmented fungal structures by histopathology.

The dematiaceous fungi are found throughout the world in soil and decaying vegetation but appear to be especially common in tropical and subtropical regions. Most patients infected with Rhinocladiella mackenziei have been from Middle Eastern countries, including Saudi Arabia, Syria, or Kuwait [17,18,21,22], but cases have also been reported from India [23], Afghanistan [24], and Pakistan [25].

D. gallopava can causes encephalitis in turkeys, chickens, and other birds, but exposure to birds has not been linked to human disease [26-28].