Two cases of multiple subcutaneous cystic phaeohyphomycosis in immunocompromised patients with a rare causative organism.

Phaeohyphomycosis comprises a spectrum of mycotic infectious diseases caused by heterogeneous group of phaeoid fungi. A subcutaneous cystic swelling with histological hallmark of pigmented hyphae in tissues accompanied by pyogenic granuloma is diagnostic of phaeohyphomycosis. We present two cases of phaeohyphomycosis in 65- and 55-year-old male agriculturalists, who presented with multiple, cystic soft-tissue masses involving extremities. Culture was done in one case and the specific organism was identified as Aureobasidium pullulans.

What was known?

Phaeohyphomycosis belongs to the group of dematiaceous fungi, forming characteristic subcutaneous swelling clinically. They are pigmented fungi and differ from chromoblastomycosis and are seen in all regions of India.

Introduction

The term phaeohyphomycosis was first coined by Ajello et al. in 1974.[1] By broad definition, Phaeohyphomycetes are fungi that produce brown-black structures, particularly spores, at least at some period in their life cycle. Phaeohyphomycosis is an infection caused by dematiaceous fungi involving skin, subcutis, paranasal sinuses, brain and other viscera.[23] The term subcutaneous phaeohyphomycosis is applied to involvement of skin and subcutaneous tissue and is characterized by a nodular or cystic lesion. Here we report two cases of phaeohyphomycosis that involved multiple sites and in one case an uncommon organism of the group i.e. Aureobasidium pullulans was cultured from the lesion.

Case Reports

Case 1

This was a case of a 65-year-old male, a farmer by occupation and a known diabetic of 5 years duration, who presented with multiple, non-tender swellings in left leg and right hand of 4 years and 6 months duration respectively. On admission, the leg swelling measured 6 cm × 6 cm and was seen discharging pus [Figure 1]. Swelling in the hand was multiple and nodular and measured 3 cm × 4 cm [Figure 2]. Serological tests were found to be negative for syphilis and human immunodeficiency virus (HIV). The sugar level was found to be 351 mg/dl. The lesion was excised and sent for histopathological examination.

Figure 1

Left leg swelling measuring 6 cm × 6 cm and discharging pus

Figure 2

Multiple, nodular right hand swelling measuring 3 cm × 4 cm

Case 2

A 55-year-old male agriculturist presented with painless swellings over left elbow of 2 years duration, right heel of 1 year duration and right leg of 2 months duration. Patient was not a diabetic. A local examination showed nodular swelling of 6 cm × 4 cm × 3 cm over right leg, 4 cm × 3 cm × 3 cm swelling over left elbow [Figure 3] and a cystic swelling over heel about 5 cm × 4 cm × 3 cm [Figure 4]. Serological tests were found to be positive for hepatitis C virus and hepatitis B surface antigen and negative for syphilis and HIV. The lesions were excised and sent for histopathological examination.

Figure 3

Left elbow swelling measuring 4 cm × 3 cm × 3 cm

Figure 4

Cystic swelling over right heel about 5 cm × 4 cm × 3 cm

In both cases, there was no regional lymphadenopathy. Complete hematological investigations were within normal limits. X-ray showed soft-tissue swelling with no evidence of involvement of underlying bone.

Pathology

Excised surgical specimens from both the cases were cystic masses ranging in size from 4 to 6 cm with smooth gray-white external surface [Figure 5]. Cut surface showed uniloculated or biloculated cysts with thin walls measuring 1-2 mm with yellowish, necrotic material adherent to the walls. Lumen contained gray-yellow gelatinous material [Figure 6]. Histological examination revealed a chronic abscess cavity containing necrotic debris and neutrophils. Cyst wall showed lymphocytes and multinucleated giant cells among other inflammatory cells. Round to oval thick walled brown cells with septate hyphae were seen intra and extracellularly [Figure 7]. The giant cells contained single or groups of organisms [Figure 8]. In essence, the microscopy showed a suppurative granuloma caused by pigmented fungi with septate hyphae and yeast forms.

Figure 5

Cystic mass 6 cm × 4 cm × 3 cm with smooth gray-white external surface

Figure 6

Cut surface showing thin, yellow wall with greyish, gelatinous material in the lumen

Figure 7

Intra and extracellular, round to oval, thick walled brown cells with septate hyphae (H and E, ×40)

Figure 8

Giant cells contained single or groups of organisms (H and E, ×40)

Microbiology

In the second case, initial potassium hydroxide preparation identified branched, septate, hyaline hyphae. Culture colonies appeared on Sabouraud's dextrose agar, which were velvety, elevated dark brown to black with black pigmentation on reverse.

Lactophenol cotton blue preparations revealed septate, thick walled, dematiaceous hyphae forming arthroconidia along with delicate, hyaline, thin walled septate hyphae with few elliptical conidia [Figure 9]. Malachite Green preparations highlighted the spores [Figure 10].

Figure 9

Lactophenol cotton blue preparation - showing septate, thick walled, dematiaceous hyphae forming arthroconidia, and few elliptical conidia

Figure 10

Malachite Green preparation - highlighting the spores

With the above features, a diagnosis of subcutaneous phaeohyphomycotic cyst was made and the specific organism was identified as A. pullulans in the second case.

Discussion

Dematiaceous fungi include three different types of infection, i.e. phaeohyphomycosis, chromomycosis and mycetoma and their distinguishing pathologic features are summarized in Table 1. Unlike chromomycosis or mycetoma, there are neither muriform cells nor grains in phaeohyphomycosis.[45] Phaeohyphomycosis is a mycosis that commonly presents as solitary cyst in the distal parts of extremities. Some cutaneous lesions may be nodular or verrucous.[6] It is often seen in immunocompetant individuals, but immunocompromise increases the risk for infection with less pathogenic organisms[7] and may also cause systemic disease.[8] Traumatic implantation of wood splinter or vegetable matter are considered to be the cause in many cases of phaeomycosis.[9] More than 130 fungal species belonging to 70 diverse genera have been reported as causative agents in humans and animals.[10] In India, the climate ranges from tropical to temperate and the disease has been reported from extreme north to south except for the western region.[2] Males are commonly affected due to their outdoor occupation. Aureobasidium is a dematiaceous fungus commonly isolated from soil and the indoor air environment. This genus includes 14 species, among which A. pullulans is the only well-known pathogen causing subcutaneous infection or phaeohyphomycosis. Colony of A. pullulans on aging becomes black and velvety. Blastoconidia (hyaline hyphae) are pale in color. They appear hyaline at the beginning and get dark brown on aging. A. pullulans has a worldwide distribution and it is usually isolated as saprophyte. However, it has also been reported as a causative agent of phaeohyphomycosis. In our case, the occupation of agriculture with much exposure to soil and trauma is probably the cause for multiple lesions in different sites and our case also shows a rare subgroup namely A. pullulans as the causative organism, which is hitherto not reported in Western literature, but has been reported from India.

Table 1

Pathologic differences between phaeohyphomycosis and other dematiaceous fungi

What is new?

Phaeohyphomycosis commonly presents as solitary cyst and the causative organisms are Bipolaris, Curvularia. In our cases, the lesion was multiple and in one case a rare causative organism namely “Aureobasidium pullulans” hitherto undescribed in western literature was found to be the cause.