Chromoblastomycosis is a chronic and progressive granu-lomatous cutaneous mycosis caused by pigmented fungi. Fungal inoculation typically occurs at the site of traumatic skin injury with lesions manifesting weeks to months after trauma. The infection commonly occurs in the exposed parts of the body, such as the lower and upper limbs^1-3. Clinical pre- sentation includes the development of nodules and verrucous plaques that eventually undergo ulceration⁴. Chromoblasto- mycosis is most prevalent in tropical and subtropical regions, but only a few cases have been reported in Korea^5,6. We report a 68-year-old man with chromoblastomycosis, notable for its occurrence in an unusual area, such as the back, with skin lesions resembling a cutaneous abscess.

A 68-year-old male farmer presented with two asymp- tomatic erythematous nodules on the left part of the upper back that had been present for 7 months (Fig. 1). His past medical history was unremarkable and there was no history of trauma. He was earlier diagnosed as a case of cutaneous abscess at another clinic and underwent incision and drain- age with empirical antibiotic therapy. However, the lesions continued to persist. Consequently, a punch biopsy was performed to rule out infectious disease. Histopathological examination revealed hyperkeratosis, parakeratosis, marked acanthosis, pseudoepitheliomatous epidermal hyperplasia, and intraepidermal microabscesses in the epidermis. A lichen- oid granulomatous inflammatory pattern was observed in the dermis with the presence of neutrophilic microabscesses in the granulomatous area (Fig. 2A). Additionally, there were prominent, golden-brown thick-walled, ovoid spores, resembling "copper pennies" (Fig. 2B). The presence of fungi was confirmed by Grocott's methenamine silver (GMS) and Periodic acid-Schiff (PAS) staining (Fig. 2 C and D). Two weeks later, colonies were observed on Sabouraud's dextrose agar (SDA) at room temperature. The colonies were dark green, and the reverse view was black. Microscopic examination of colonies cultured in SDA and stained with lactophenol-cotton blue revealed erect, septate, and sympodial conidiophores. The distal ends of the conidiophores were slightly swollen to form single-celled conidia, that became branched (Fig. 3 A and B). Fonsecaea pedrosoi was identified based on the typical histomorphological characteristics and fungal culture. Following the diagnosis of chromoblastomycosis due to F. pedrosoi, the patient was prescribed itraconazole 200 mg daily, topical isoconazole, and cryotherapy with liquid nitrogen. After 4 months of treatment, the lesions showed improvement.

Figure 1. Two erythematous bean to coin-sized abscesses on the left upper back

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Figure 2. (A) Histopathological examination revealed hyperkeratosis, parakeratosis, marked acanthosis, pseudoepitheliomatous epidermal hyperplasia, and intraepidermal microabscess in the epidermis. In the dermis, there was a lichenoid granulomatous in-flammatory pattern (H&E, ×40). (B) Sclerotic bodies were observed within the granulomatous inflam- mation, as indicated by arrows (H&E, ×400). (C-D) The confirmation of sclerotic bodies was achieved through GMS and PAS staining (×400).

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Figure 3. (A) F. pedrosoi cultured in Sabouraud's dextrose agar (B) Erect, conidial and symbiotic conidium, with the conidium tip slightly swollen to form single-celled conidia that become branched

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Chromoblastomycosis is a chronic cutaneous and sub- cutaneous fungal infection primarily caused by melanized fungi. These fungi are characterized by their brown pigmen- tation due to the production of melanin. The fungi often reside in the soil, wood, and plants. Chromoblastomycosis occurs worldwide, but is more prevalent in tropical and temperate regions, predominantly affecting individuals with occupational exposure to the fungi in the environment⁶. At least 41 species of fungi have been reported to cause chromo- blastomycosis⁵. In Korea, a few types such as F. monophora, F. pedrosoi, Phialophora richardsiae, Phialophora verrucosa, and Rhinocladiella aquaspersa, have been reported, and the number of cases reported in the literature is small compared to other countries^5-8.

Chromoblastomycosis is indeed considered an occupational disease, particularly prevalent among agricultural workers¹. The infection is attributed to the invasion of the skin by the fungus at the site of trauma, leading to the development of skin lesions. These lesions typically occur in the exposed areas that are unprotected by clothing. The arms, and especially the lower extremities are the most commonly involved sites in cases of chromoblastomycosis^1-3. However, not all patients may recall a specific history of trauma at the site of the lesion⁷. This may be attributed to a prolonged latency period⁹.

The lesions can manifest in various forms, including nodular, tumorous, verrucous, cicatricial, and plaque lesions⁴. The diverse nature of these skin lesions may pose a diagnostic challenge. Thus, histological and mycologic examinations are imperative to identify the fungal infection. The typical histo- logical characteristics of chromoblastomycosis are pseudo- epitheliomatous epidermal hyperplasia, intraepidermal micro- abscesses, and mixed granuloma. Dark brown, ovoid, or spherical spores resembling "copper pennies" indicate mela- nized fungi as the causative pathogen. This appearance can be easily visualized by Hematoxylin and Eosin staining. Additionally, special stains such as GMS and PAS can help support the diagnosis by highlighting the fungal elements¹⁰. These histopathological features are crucial for distinguishing chromoblastomycosis from other skin conditions.

Initial identification of putative species in chromoblasto- mycosis is often performed using mycological and morpho- logical methods. The species of Fonsecaea display erect, septate, and sympodial conidiophores that are extensively branched at their apices. Phialophora verrucosa has a mono- morphic morphology characterized by flask-shaped phialides. Rhinocladiella aquaspersa features erect, brown, septate conidiophores, bearing conidia at their terminal parts¹¹. These traditional methods of examining morphological characteristics are time-consuming. However, the advances in diagnostic technology have enabled rapid identification of the fungal species. Molecular techniques, such as gene sequencing analysis are used for the definitive identification of fungal species^12,13. A limitation of this study is that molecular analysis for identifying the causative fungus was not performed. The morphological characteristics observed in this case were consistent with Fonsecaea species. Although F. monophora and F. pedrosoi are morphologically very similar, F. pedrosoi was identified as the causative agent in this case based on the fact that F. pedrosoi generally has slightly shorter conidial chains and slightly longer denticles than F. monophora¹².

To the best of our knowledge, 10 cases of chromoblasto- mycosis have been reported in Korea (Table 1). In these cases, the lesions predominantly manifested in the exposed parts of the body, exhibiting diverse clinical presentations. Our patient presented with a nodule resembling a cutaneous abscess, obscuring the diagnosis. Notably, only two previous cases with lesions in the non-exposed areas (abdomen and breast) have been reported in Korea^8,14. This case represents the first instance of chromoblastomycosis caused by F. pedrosoi in non-exposed areas. Despite the denial of any history of trauma, the possibility of chromoblastomycosis was consid- ered, especially given his occupation as a farmer.

In conclusion, we suggest that the possibility of chromo- blastomycosis should be considered in individuals presenting with skin lesions, especially those with an occupational back- ground as farmers. Early recognition and diagnosis are pivotal for effective management, and conducting a biopsy, as exemplified in this case, is a crucial step for accurate diagnosis. The authors report this rare and interesting case along with a review of pertinent literature.