Subcutaneous phaeohyphomycosis caused by Phaeoacremonium rubrigenum in an immunosuppressed patient.

BACKGROUND

Phaeohyphomycosis refers to infection by dematiaceous fungi with pigmented hyphae or yeast-like cells in the tissue. In humans, this disease is usually considered to be an opportunistic infection. The causal agents of phaeohyphomycosis include numerous species belonging to different genera and they are increasing as a result of the development of intensive medical therapy.

OBSERVATION

We report the case of a 61-year-old Japanese female under corticosteroid treatment for malignant rheumatoid arthritis. An asymptomatic subcutaneous tumor developed on the back of her left foot. Histological examination of the excised material revealed mixed cell granuloma (H&E) and the presence of branched hyphal elements (periodic acid-Schiff). A fungus grown in pure culture was identified as Phaeoacremonium rubrigenum.

CONCLUSION

The hyphomycete genus, Phaeoacremonium, was proposed in 1996 by Crous et al. Three species belonging to this genus have been isolated from clinical specimens: P. inflatipes, from a human toenail, human synovial fluid and human mycetoma of the foot, P. parasiticum, from a subcutaneous lesion on a kidney transplant patient and several other sources, and P. rubrigenum, from a human patient with pneumonia. To our knowledge, however, this is the first report of phaeohyphomycosis caused by Phaeoacremonium rubrigenum.