Semantics--tinea versus pityriasis versicolor and Pityrosporum orbiculare versus Malassezia furfur. Which is proper?

Cutaneous defenses against dermatophytes and yeasts

Predispositions to the superficial mycoses include warmth and moisture, natural or iatrogenic immunosuppression, and perhaps some degree of inherited susceptibility. Some of these infections elicit a greater inflammatory response than others, and the noninflammatory ones are generally more chronic. The immune system is involved in the defense against these infections, and cell-mediated immunity appears to be particularly important. The mechanisms involved in generating immunologic reactions in the skin are complex, with epidermal Langerhans cells, other dendritic cells, lymphocytes, microvascular endothelial cells, and the keratinocytes themselves all participating in one way or another. A variety of defects in the immunologic response to the superficial mycoses have been described. In some cases the defect may be preexistent, whereas in others the infection itself may interfere with protective cell-mediated immune responses against the organisms. A number of different mechanisms may underlie these immunologic defects and lead to the development of chronic superficial fungal infection in individual patients. Although the immunologic defects appear to be involved in the chronicity of certain types of cutaneous fungal infections, treatment of these defects remains experimental at the present time.

A reevaluation of the genus Malassezia by means of genome comparison

Results of a study of the genus Malassezia on the basis of genome characters confirm that two species should be maintained, M. furfur and M. pachydermatis. The two forms associated with skin disease, frequently referred to as Pityrosporum orbiculare and P. ovale, were found to be synonymous, the name M. furfur having priority. Malassezia pachydermatis, hitherto regarded as a strictly zoophilic species, may also be found on humans.

Epidemiology, diagnosis, and management of Malassezia furfur systemic infection

Malassezia furfur, a normal skin flora yeast, generally associated with very mild superficial skin infections, has become an opportunistic pathogen in patients with deep-line vascular catheters. The use of intravenous fat emulsions appears to have altered the microenvironment of the catheter and allowed colonization and subsequent infection. Dissemination of the organism appears to be limited to the lungs, which may have been previously altered by vascular lipid deposition. Because of the serious underlying disease(s) of patients with M. furfur catheter sepsis, it is difficult to determine the exact role of the organism in the overall status of the patients. At the very least, however, catheter removal or discontinuance of the fat emulsion therapy may be required. Antifungal therapy without either of these two steps has not been shown to be efficacious. Physicians must maintain a high index of suspicion of M. furfur catheter sepsis in the appropriate clinical setting, and laboratory investigators must be prepared to provide appropriate diagnostic methods.