Pheohyphomycotic cyst.

Sir,

Pheohyphomycosis is an affection characterized by dematiaceous yeast-like cells, hyphae and pseudo-hyphae in the affected tissue.[1] It can occur in any climatic region, but it is more frequent in the tropics. The involvement of skin and subcutaneous tissue is known as subcutaneous pheohyphomycosis.[12] The term “phaeohyphomycosis” was coined by Ajello et al. in 1974.[3] These fungi often infect patients who are not overtly immunocompromised and therefore may be encountered in a wide variety of cases.

A 60-year-old housewife presented to dermatology outpatient department of a tertiary care hospital with a smooth painless swelling on the dorsal aspect of left foot of two years duration. The patient gave a history of minor trauma to the involved foot with a wooden splinter while doing household chores two months prior to occurrence of lesions. There was no history of discharge from the swelling. Her medical history revealed that she was hypertensive and was suffering from degenerative joint disease limited to both the knees. Her general and systemic examination was remarkably normal. Complete haemogram, routine biochemistry, urinalysis, chest roentgenogram and cardiac evaluation were normal. The tuberculin skin test was negative.

Cutaneous examination revealed a well-defined smooth swelling on the dorsum of left foot with intact overlying skin with a groove in between clinically looking like a loculated cystic swelling [Figure 1]. Radiological examination including ultrasound suggested a subcutaneous swelling without bony involvement. There was no evidence of lymphangitic spread or regional lymphadenopathy. Histopathological examination of biopsy from left foot swelling showed a cystic structure lined by a granulomatous inflammatory infiltrate. Culture from the tissue sample showed no growth on Sabourauds dextrose agar. Gomori Methenamine Silver (GMS) staining of biopsy tissue revealed multiple black staining hyphae with irregular branching [Figure 2]. Masson-Fontana staining showed multiple hyphae containing melanin, consistent with the diagnosis of pheohyphomycotic cyst. Species identification could not be done due to lack of resources at our end.

Figure 1

A smooth lobulated swelling on the dorsum of left foot

Figure 2

Gomori Methenamine Silver stained section showing black staining hyphae with irregular branching along the cyst wall (×20)

With a working diagnosis of pheohyphomycosis, the patient was started on oral saturated solution of potassium iodide in the concentration of 1 gm/ml along with itraconazole 200 mg twice daily along with monitoring of liver enzymes. The patient was lost to follow-up after three months of therapy due to personal difficulties.

Phaeohyphomycosis is a rare infection caused by dematiaceous fungi, of which most commonly incriminated are Exophiala, Alternaria, Bipolaris, Wangiella, and Curvularia.[4]

The clinical manifestations of pheohyphomycosis can be divided into four categories: (i) superficial form, including “black piedra” and “tinea nigra” representing infection of superficial layers of skin; (ii) cutaneous and corneal form, which includes dermatomycosis. onychomycosis and mycotic keratitis; (iii) subcutaneous form comprising of cystic lesions which usually follow after a traumatic event; (iv) systemic or invasive form, in which there is dissemination to other organs; this form occurs in immunocompromised patients and organs commonly involved include lungs, brain, paranasal sinuses and rarely, the skin.[5]

Subcutaneous infection is caused by traumatic inoculation of the organisms and is usually observed in exposed areas of skin surface. Although diagnosis relies on culture of the organism or demonstration of pigmented hyphae in tissue biopsy, in some cases, cystic lesions are caused by nonpigmented hyphae and the condition is then termed as hyalohyphomycotic cyst.[2] In our patient, histopathology showed a cystic structure in the deep dermis and the wall of the cyst lined by a suppurative granulomatous infiltrate with multiple pigmented hyphae along the cyst wall. Hyphal elements could be clearly visualized on GMS staining. To differentiate from hyalohyphomycosis (nonpigmented hyphae), Masson-Fontana stain can be utilized to demonstrate pigment melanin in the fungus.[67] In our case both GMS stain and Masson-Fontana stain confirmed the diagnosis of phaeohyphomycosis.

Subcutaneous disease can be managed by surgical excision which is the chief modality of treatment with or without antifungal therapy.[3] Nevertheless; itraconazole at a dose of 200 mg twice daily provided some respite from surgical management in an individual who was unwilling to tolerate extensive debulking surgery.[8]