[Cutaneous infection due to Fusarium oxysporum in a female diabetic: molecular biological detection of the mold from formalin-fixed paraffin embedded tissue using sequencing of the ITS region of the rDNA]

Abstract

Background: Skin lesions due to Fusarium spp. occur either secondarily following hematological spread in systemic infection or represent primary cutaneous infections following traumatic inoculation.

Case report: A 34-year-old woman with insulin-dependent diabetes mellitus presented with a most likely posttraumatic leg ulcer present for 4 weeks. The ulcer showed superficial necrosis with cellular debris, neutrophils, and leukocytoclasia. Septate hyphae were detected both in the necrotic area and between the collagen fibers on initial H & E stained sections. Using PAS and Grocott-Gomori silver staining, the dichotomous branching hyphae were clearly visible. Unfortunately, cultural detection of the fungi was impossible. After extraction and purification of the fungal DNA from formalin-fixed and paraffin embedded (FFPE) tissue sections, the amplification of the ITS region of rDNA was done. Using sequencing and comparison with reference sequences of a gene bank, Fusarium oxysporum was identified.

Therapy: Therapy was performed by surgical excision of the entire ulcer followed by topical antiseptic treatment and wound conditioning. No systemic antifungal treatment was given. The lesion healed without any problems.

Discussion: Cutaneous fusarium infections are rare but emerging opportunistic infections. Histological examination represents the quickest diagnostic method for detection of the fungal infection. An alternative approach represents the species identification based on molecular techniques.