Cutaneous phaeohyphomycosis caused by a rare fungal pathogen, Hormonema dematioides: successful treatment with ketoconazole

Melanized fungi in human disease

Melanized or dematiaceous fungi are associated with a wide variety of infectious syndromes, including chromoblastomycosis, mycetoma, and phaeohyphomycosis. [corrected]. Many are soil organisms and are generally distributed worldwide, though certain species appear to have restricted geographic ranges. Though they are uncommon causes of disease, melanized fungi have been increasingly recognized as important pathogens, with most reports occurring in the past 20 years. The spectrum of diseases with which they are associated has also broadened and includes allergic disease, superficial and deep local infections, pneumonia, brain abscess, and disseminated infection. For some infections in immunocompetent individuals, such as allergic fungal sinusitis and brain abscess, they are among the most common etiologic fungi. Melanin is a likely virulence factor for these fungi. Diagnosis relies on careful microscopic and pathological examination, as well as clinical assessment of the patient, as these fungi are often considered contaminants. Therapy varies depending upon the clinical syndrome. Local infection may be cured with excision alone, while systemic disease is often refractory to therapy. Triazoles such as voriconazole, posaconazole, and itraconazole have the most consistent in vitro activity. Further studies are needed to better understand the pathogenesis and optimal treatment of these uncommon infections.

Posaconazole therapy of disseminated phaeohyphomycosis in a murine model

Immunocompetent (nu/+) and athymic (nu/nu) BALB/c mice were infected intravenously with Wangiella dermatitidis and treated with posaconazole. Posaconazole reduced the counts in tissues and prolonged survival. Of particular interest, posaconazole reduced the counts of this neurotropic pathogen in the brain.

Developments in fungal taxonomy

Fungal infections, especially those caused by opportunistic species, have become substantially more common in recent decades. Numerous species cause human infections, and several new human pathogens are discovered yearly. This situation has created an increasing interest in fungal taxonomy and has led to the development of new methods and approaches to fungal biosystematics which have promoted important practical advances in identification procedures. However, the significance of some data provided by the new approaches is still unclear, and results drawn from such studies may even increase nomenclatural confusion. Analyses of rRNA and rDNA sequences constitute an important complement of the morphological criteria needed to allow clinical fungi to be more easily identified and placed on a single phylogenetic tree. Most of the pathogenic fungi so far described belong to the kingdom Fungi; two belong to the kingdom Chromista. Within the Fungi, they are distributed in three phyla and in 15 orders (Pneumocystidales, Saccharomycetales, Dothideales, Sordariales, Onygenales, Eurotiales, Hypocreales, Ophiostomatales, Microascales, Tremellales, Poriales, Stereales, Agaricales, Schizophyllales, and Ustilaginales).

Fatal Hormonema dematioides peritonitis in a patient on continuous ambulatory peritoneal dialysis: criteria for organism identification and review of other known fungal etiologic agents

We report a fatal case a fungal peritonitis caused by the yeast-like dematiaceous mould Hormonema dematioides in a 45-year-old woman. The woman had a 13-year history of insulin-dependent diabetes mellitus and had been on continuous ambulatory peritoneal dialysis for chronic renal failure. H. dematioides was repeatedly isolated from the dialysate culture specimens collected on days 3, 9, 16, and 20 of her hospital stay. Preliminary culture reports on day 7 of the growth of a yeast-like fungus, a probable Candida species, prompted the administration of fluconazole (FLU). Intraperitoneal and intravenous FLU failed to eliminate the mould, and the patient expired on day 21 of her hospital stay. We use this case to present what appears to be the first report of fungal peritonitis due to H. dematioides, to provide laboratorians with criteria for differentiating this organism from the similar mould Aureobasidium pullulans and from various yeast genera, and to provide a review of known fungal taxa inciting peritonitis.

Conidiogenesis, nutritional physiology and taxonomy of Aureobasidium and Hormonema

Diagnostic criteria for the distinction of the slightly osmophilic species, Aureobasidium pullulans, and the opportunistic pathogen on conifers, Hormonema dematiodies, are provided. Reliable identification requires a combination of characters of conidiogenesis, expansion growth and assimilative abilities. Relationships with species of Kabatiella, and with the teleomorph genera Pringsheimia, Dothidea and Dothiora, all having Dothiora, all having Hormonemia-like cultural states, are discussed. An identification key is provided.

Phaeohyphomycosis caused by Exophiala jeanselmei treated with itraconazole

Phaeohyphomycotic cysts developed on the right knee of a 72-year-old woman undergoing immunosuppressive treatment for ulcerative colitis 6 years after accidental inoculation of soil in a bicycle accident. The lesions were red, firm, slightly raised, 0.5-1 cm in size and completely asymptomatic. The diagnosis was made by histopathological examination of three excised cysts and by repeated isolation of Exophiala jeanselmei in pure culture. The excised cyst walls contained large numbers of dematiaceous fungal elements in the form of hyphae, yeast-like cells and some cells dividing internally by a transverse septum. The patient was treated with 200 mg of itraconazole daily, but the treatment had to be stopped because of severe side-effects after 6 weeks. Histologically the cysts were cleared of dematiaceous elements, but E. jeanselmei could still be isolated from one of two skin biopsies 1 month after the end of therapy.

Cutaneous and subcutaneous phaeohyphomycosis caused by Exserohilum rostratum

Phaeohyphomycosis of the skin caused by Exserohilum is rare. Four cases have been reported; all were subcutaneous in type and all were caused by Exserohilum rostratum. We report two types of skin infection, cutaneous and subcutaneous, that were caused by E. rostratum in two immunocompromised men. Pleomorphic fungal elements were noted within the dermal suppurative and granulomatous infiltrate in case 1 and only within the central hyperkeratotic horny layer of a porokeratosis-like lesion in case 2. E. rostratum was isolated in both cases. Case 2 represents the first documented case of cutaneous Exserohilum phaeohyphomycosis. The clinical and histologic features in this case resembled superficial porokeratosis. To the best of our knowledge these findings have not been reported previously in fungal infections of the skin. The ambiguous terminology that is used in the classification of phaeohyphomycosis is also discussed.

The medically important dematiaceous fungi and their identification

Dematiaceous fungi include a large group of organisms that are darkly pigmented (dark brown, olivaceous, or black). In most cases the pigment is melanin, and specifically, dihydroxynaphthalene melanin. The diseases produced include chromoblastomycosis, eumycotic mycetoma, and phaeohyphomycosis. Phaeohyphomycosis is a new classification for a diverse group of previously known entities grouped together on the basis of finding dematiaceous hyphal and/or yeast-like forms in tissue; tissue involvement may be superficial, cutaneous and corneal, subcutaneous, or systemic. Identification of these fungi is based mostly upon morphology. Important structures include annellides (Phaeoannellomyces, Exophiala), phialides (Phialophora, Wangiella), adelophialides (Phialemonium without collarettes, Lecythophora with collarettes), differentiation of conidiophores (Xylohypha versus Cladosporium) and conidial hilum, septation and germination (Bipolaris, Drechslera, Exserohilum). Useful laboratory tests include the 12% gelatin test (controversial), nitrate assimilation (W. dermatitidis is negative, most other species are positive), and determination of temperature maxima (especially 37 degrees C for E. jeanselmei, 40 degrees C for W. dermatitidis and B. spicifera, 42 degrees C for X. bantiana, and 45 degrees C for Dactylaria constricta var. gallopava and Scedosporium inflatum).