Phaeohyphomycosis in a Kidney Transplant Recipient

A 60-year-old male farmer underwent living-related kidney transplantation 13 months ago, with his wife as the donor. Induction therapy included basiliximab (total dose, 40 mg), followed by maintenance immunosuppression with tacrolimus, mycophenolate mofetil, and steroids.

He presented with a painless, ulcerated exophytic lesion with areas of necrosis over the plantar aspect of the left great toe [Figure 1a]. At presentation, graft function was stable (serum creatinine, 1.2 mg/dL), and the tacrolimus trough (C₀) level was 7.7 ng/mL.

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Figure 1:

(a) Ulcerated, exophytic lesion with necrosis on the plantar aspect of the left great toe (white arrow). (b) Hematoxylin and eosin stain (400x) showing a suppurative abscess (orange arrow), pigmented septate hyphae and yeast-like forms (pink arrows), and a multinucleated giant cell (green arrow).

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Excision biopsy revealed mixed inflammatory infiltrates, areas of necrosis, and pigmented fungal elements [Figure 1b], consistent with phaeohyphomycosis. Systemic involvement was excluded. Treatment with oral voriconazole (200 mg twice daily) was initiated, and the tacrolimus dose was adjusted.

Phaeohyphomycosis is an uncommon fungal infection caused by dematiaceous fungi and occurs predominantly in immunocompromised individuals.¹ Cutaneous lesions frequently mimic neoplasms or chronic infections, often resulting in delayed diagnosis.² The hallmark of this infection is its filamentous morphology; unlike chromoblastomycosis, which presents as round, thick-walled “copper penny” sclerotic bodies, phaeohyphomycosis features distinct hyphal elements that are visible without special stains due to their innate melanin.³ Management involves surgical excision combined with systemic antifungal therapy.⁴