Blastomycosis presenting as solitary nodule: a rare presentation.

Blastomycosis is a chronic granulomatous and suppurative mycosis, caused by Blastomyces dermatitidis, which in the great majority of cases presents as a primary pulmonary disease. Primary cutaneous blastomycosis is very rare. We present a 57-year-old female patient with a solitary, slowly progressive nodule over upper lip of 2½ months duration. Initially, differential diagnosis of cutaneous leishmaniasis, pyoderma and deep mycoses were entertained. Slit smear preparation was suspicious of deep mycotic infection which was subsequently confirmed by biopsy and culture.

Introduction

Blastomycosis is an uncommon, chronic granulomatous and suppurative mycosis caused by Blastomyces dermatitidis. There are three forms of blastomycosis: pulmonary, disseminated and primary cutaneous blastomycosis. The skin is the most common site for dissemination, followed by bone, genitourinary tract, and central nervous system.[12] Primary cutaneous blastomycosis is rare and mostly occurs as a laboratory or autopsy room infection.[3] Blastomycosis is rare in India.

We report a case of cutaneous blastomycosis presenting as a solitary nodule. The case is reported due to its rarity and dramatic response to oral itraconazole therapy.

Case Report

A 57-year-old female presented with a single painful nodule over upper lip of 2½ months duration. The lesion started as a group of vesicles and pustules and later it turned into a nodule with slow enlargement. There was no history of trauma or any insect bite. She had history of rheumatoid arthritis for last 15 years and was on injection methyl prednisolone acetate (40 mg/ml) 2 ml every fortnight, oral prednisolone 20 mg and NSAIDs daily for last 1 year.

On examination, the patient had a single erythematous indurated nodule of size 1 × 1 cm2, over upper lip [Figure 1]. It was studded with pustules and had lobulated surface. Regional lymph nodes were not enlarged. There were no other significant findings on general, systemic, or dermatological examination.

Figure 1

Nodule over upper lip before treatment

Differential diagnosis of cutaneous leishmaniasis, pyoderma, deep mycoses were considered.

Therapy was initiated by systemic and topical antibiotics but the lesion failed to respond. Intralesional injection of sodium stibogluconate twice fortnightly was also tried with no response.

Routine laboratory investigations like complete blood count, urine examination, liver function test, renal function tests were normal. X-ray chest was normal. Slit smear was prepared from the lesion and on staining with giemsa stain, small round to oval yeast like structures were seen. KOH preparation from the pus showed spherical yeast with broad based buds. On histopathological examination hyperkeratotic stratified superficial squamous epithelium with epitheloid cells, histiocytes and Langerhans giant cells with some oval to round bodies were seen. It was suggestive of infective granulomatous lesion. White to tan colony was grown on Sabourauds dextrose agar within 14 days. When the culture was fully grown, blastomycosis was confirmed based on the macroscopic and microscopic appearance of the colony [Figures 2–4]. Considering the diagnosis of localized cutaneous blastomyosis based on KOH smear and morphology of growing colonies, patient was given itraconazole 100 mg BD orally for 3 months. Dramatic improvement was seen within 4 weeks of treatment. The size of the lesion was reduced to half, pustules dried up, and the nodule was less eythematous and less indurated. Complete clearance of the lesion was seen by 3 months [Figure 5].

Figure 2

Colony of Blastomyces

Figure 4

LCB mount showing typical yeasts with broad based buds (×1500)

Figure 5

Complete clearance of the lesion after treatment

LCB mount of blastomyces showing conidia (×400)

Discussion

Blastomycosis is found chiefly in North America but cases have been reported from Africa, Europe, and Asia. It is rare in India, but cases have been reported.[4] The incidence of infections tends to be highest in rural areas and in agricultural workers.

Cutaneous blastomycosis can occur as primary cutaneous blastomycosis or as a manifestation of disseminated extrapulmonary blastomycosis. Skin lesions in the disseminated form may be single or multiple, often symmetrical and usually on the trunk.[5] Primary cutaneous blastomycosis is very rare and follows trauma to skin and introduction of fungus.[5]

After inoculation, an erythematous indurated area with a chancre appears in 1-2 weeks with associated lymphangitis and lymphadenopathy. There is a strong tendency toward spontaneous recovery.[5]

Clinically, cutaneous blastomycosis may be mistaken for tuberculosis, bacterial pyoderma, squamous cell carcinoma, tertiary syphilis.[4] Diagnosis of skin lesion is established by culture or biopsy.[5]

Amphotericin B is widely used for widespread disseminated forms of blastomycosis.[6] Itraconazole is drug of choice for cutaneous blastomycosis.[7] Ketoconazole and fluconazole are also effective. Surgical procedures such as excision and I and D can be done when needed. Awareness of this condition in patients not responding to routine conventional therapy for pyodermas may help initiate appropriate laboratory investigations for earlier diagnosis and successful treatment.