Hyperkeratotic Warty Skin Lesion of Foot Caused by Fusarium oxysporum.

Fusarium species are common soil-inhabiting organisms and plant pathogens. Human infections are usually precipitated by local or systemic predisposing factors, and disseminated infection is associated with impaired immune responses. Skin infections caused by Fusarium spp. include keratitis, onychomycosis, mycetoma, painful discrete erythematous nodules. Hyperkeratotic skin lesions caused by Fusarium spp. are, however, rarely reported. We report a case of hyperkeratotic verrucous warty skin lesion in the foot of a 50-year-old immunocompetent male, farmer by occupation.

What was known?

Hyperkeratotic lesions caused by Fusarium spp are very rare, and have been described in people with some form of immunodeficiency.

Introduction

Fusarium species are common soil-inhabiting organisms and plant pathogens. Among immunocompetent patients, tissue breakdown (trauma, severe burns or foreign body) is the risk factor for fusariosis.[12] Superficial infections commonly caused by Fusarium spp. include keratitis, onychomycosis, and mycetoma while cellulites, erythematous pustules, painful discrete erythematous nodules, and ulcerative lesions are less common.[3-5] Hyperkeratotic skin lesions caused by Fusarium spp. are, however, rarely reported.[67]

Case Report

A 50-year-old male, farmer by occupation, used to work barefoot in the fields, developed cracked heels. The lesion began in the form of small painless papules and slowly progressed to painful hyperkeratotic warty lesion over a period of 1 year. There was no discharge of pus or granules from the lesion.

Examination of the skin lesion showed hyperkeratotic, verrucous skin lesions, firm to touch and surrounded by erythema [Figure 1]. No sinus or grains could be seen. No other lesion was seen at any other site in the body, ruling out disseminated infection. No lymphadenopathy was noted, and the physical examination was normal. A differential diagnosis of chromoblastomycosis, tuberculosis verrucosa cutis, sporotrichosis, and psoriasis were kept in mind, and the patient was investigated.

Figure 1

Heel of the patient showing hyperkeratotic warty lesion

Skin biopsy was taken from the lesion. Direct KOH mount of the lesion showed septate branching hyaline hyphae. Culture done on Sabourauds Dextrose Agar (SDA) with and without cycloheximide revealed whitish-grey cottony colonies after 5 days of incubation at 22°C. Lactophenol cotton blue mount from the colonies showed branched septate hyphae with large sickle-shaped macroconidia and single-celled microconidia, suggestive of Fusarium spp. On slide culture, the species was found to be Fusarium oxysporum [Figure 2]. On histopathology, hyperkeratosis with fungal hyphae were detected [Figure 3]. Ziehl Neelsen staining did not show any acid-fast bacilli. Blood culture of the patient for fungal pathogens was negative. X-ray foot of the patient did not reveal any bony invasion. The patient was not immunocompromised as suggested by a negative HIV status, normal neutrophil count and blood sugar levels, no evidence of any hematological malignancy.

Figure 2

Lactophenol cotton blue mount from the colonies on Sabourauds Dextrose Agar showing fusoid macroconidia and microconidia under ×1000 magnification

Figure 3

Histopathology photograph of skin biopsy showing fungal hyphae

The patient was put on oral itraconazole 400 mg/day therapy along with local debridement.

Discussion

Fusarium infection can present in the skin with a variety of lesions, more commonly with erythematous papules, nodules with central necrosis, and subcutaneous nodular lesions. Less frequently, cutaneous fusariosis manifests as onychomycosis, intertrigo, finger cellulitis, pustules, ecthyma gangrenosum-like lesions and mycetoma, or lesions resembling granuloma anulare or facial granuloma.[3-589] Hyperkeratotic lesions due to Fusarium spp are rarely encountered and are primarily reported from patients with some form of immunodeficiency.[67]

The patient may have acquired the fungus from the soil through cracked heels and showed slow progression of the lesion as reported in immunocompetent patients.[2] The diagnosis of Fusarium infection may be made on histopathology, fungal culture, blood culture, or serology and does not need any special investigations. The most important microscopic features in species identification on culture are the presence of fusoid macroconidia with foot cells with some type of heel and is accepted as the most definitive characteristic of the genus Fusarium.[10] In localized infections, relatively good response may be expected following appropriate surgery and oral anti-fungal therapy. The patient was started on oral itraconazole 200 mg twice daily. After 1 week of itraconazole therapy, local debridement was done. Further itraconazole was continued for 9 more weeks when hyperkeratotic lesion had subsided completely; however, the heel of the foot was still rough with few cracks. Itraconazole was further given for 2 more weeks to complete a 12-week course. Our patient responded well on local debridement and oral itraconazole therapy.

Conclusion

It is important to understand the relevance of the opportunistic fungi, such as Fusarium spp., which have emerged as human infectious agents, emphasizing the need for correct etiological identification, allowing for appropriate treatment. In our opinion, Fusarium spp can be added to the list of pathogens causing hyperkeratotic verrucous warty lesions after minor trauma in an immunocompetent host.

What is new?

Fusarium spp can cause hyperkeratotic verrucous lesions in immunocompetent people also and should be kept mind while investigating such lesions.