A Pigmented Fungal Infection Presenting Clinically as a Keloid

Summary: A 54-year-old male, with a history of end-stage renal disease and a kidney transplant, presented to the dermatology clinic for a skin examination. He was found to have a firm, smooth, hyperpigmented papule on his thigh, which was clinically consistent with a keloid. A biopsy was performed with pathology revealing pseudoepitheliomatous hyperplasia with dense dermal inflammation composed of histiocytes, lymphocytes and neutrophils with numerous pigmented spores and hyphae. Staining with GMS and PAS also highlighted the fungal organisms. This was favored to represent phaeohyphomycosis. Phaeohyphomycosis is a group of dematiaceous fungi. While both immunocompetent and immunocompromised patients may be affected, immunocompromised patients are more likely to have systemic infections, which can be fatal. Cutaneous phaeohyphomycosis often presents as a nodule or plaque. On pathology, there is suppurative and granulomatous inflammation with pigmented fungal elements. A foreign body, such as a splinter, may also be present. Fontana-Masson stain can be utilized to detect melanin if pigment is not apparent with hematoxylin and eosin. Treatment is with surgical excision and oral antifungals. It is important to be aware that this may clinically mimic a benign entity and to keep this diagnosis in mind, especially in immunocompromised patients.