CLINICAL HISTORY:

Signs and symptoms:  A 78-year-old male presented with a 2-month history of an erythematous plaque on his right hand that started after gardening. The plaque was non-pruritic and non-painful but has been draining a purulent discharge for the last six weeks. His medical history included diabetes mellitus type 2, coronary artery disease, chronic obstructive pulmonary disease, hypertension, prostate cancer, and laryngeal cancer treated with radiation.

Previous Treatment:  The plaque was treated as cellulitis with both oral and IV antibiotics for the prior two months, however it continued to enlarge.

Other information:  None

PHYSICAL EXAM:

Physical examination revealed a large indurated and hyperkeratotic erythematous plaque covering his right wrist and dorsal forearm, which expressed copious amounts of pus from sinus tracts when pressure was applied (Figure 1 and 2). There was no streaking, tenderness or arthlagia of the wrist joint.

Figure 1

Figure 2

LABORATORY TESTS:

The bacterial culture and gram stain were negative for organisms.
Fungal culture grew Pseudoallescheria boydii.

DERMATOHISTOPATHOLOGY:

In the biopsy there was a cyst like cavity in the dermis lined by fragments of epithelium suggestive of a cyst wall with an adjacent suppurative and granulomatous inflammatory cell infiltrate. Neutrophils, macrophages and multinucleated giant cells were noted in the infiltrate (figure 3). A Periodic acid-Schiff (PAS) stain highlighted fungal elements in the multinucleated giant cells as well as in the areas of abscess formation.

Figure 3

PAS

DIFFERENTIAL DIAGNOSIS:

1.   Deep fungal infection
2.   Cellulitis
3.   Foreign body granuloma
4.   Botryomycosis
5.   Soft tissue tumor

SCROLL DOWN FOR ANSWER AND DISCUSSION.

CORRECT DIAGNOSIS:

Eumycotic mycetoma

DISCUSSION:

Mycetoma is a chronic, subcutaneous, granulomatous inflammatory disease caused by either a filamentous bacteria (actinomycotic mycetoma) or true fungi (eumycotic mycetoma). It is characterized by the triad of tumefaction, granules, and draining sinus tracks which can ultimately lead to bony deformity (1). Causative organisms are usually acquired from the soil through a direct penetrating injury, often by a splinter or thorn prick (2). Our patient recalled a thorn prick while gardening two months earlier; however many patient’s do not recall any such trauma to the infection site (3).

Mycetoma can be found worldwide with the highest incidence occurring in tropical and subtropical countries. The incidence is highest in India and Sudan, and large numbers of cases have been reported in Latin America, Mexico, Venezuela, and Brazil (4). Worldwide the most common cause of eumycetoma is Madurella mycetomatis. Our patient grew Pseudoallescheria boydii from his culture, which is the most common causative organism of eumycetoma in the United States (2).

Clinically the infection usually presents on the foot (70-80%) or hand (12%) as a unilateral painless papule or subcutaneous nodule (3,2). As the infection progresses the surrounding tissue becomes swollen, forming multiple draining sinus tracks that express a purulent discharge. Within the purulent discharge are the characteristic grains, also called sclerota, which represent small fungal colonies. Deep subcutaneous abscesses eventually form which extend into the fascia, muscle, and bone, leading to deformity and disability if untreated (2). Histologically, three different types of tissue reactions have been described (3). The organisms can be highlighted with a PAS or methenamine silver stain (GMS).

Correct species identification is important to determine the correct treatment. Tissue culture is the primary method of identification. PCR is an alternate method when tissue cultures are negative (5).

TREATMENT:

The treatment of eumycetoma typically consists of antifungal treatment with either itraconazole or ketoconazole for 18-24 months or longer, combined with surgical excision and debulking (6).

REFERENCES:

1. McGinnis MR. Mycetoma. Dermatol Clin. 1996 Jan;14(1):97-104.
2. Lichon V, Khachemoune A. Mycetoma: a review. Am J Clin Dermatol. 2006;7(5):315-21.
3. Fahal AH. Mycetoma: a thorn in the flesh. Trans R Soc Trop Med Hyg. 2004 Jan;98(1): 3-11.
4. Castro LG, Piquero-Casals J. Clinical and mycologic findings and therapeutic outcome of 27 mycetoma patients from São Paulo, Brazil. Int J Dermatol. 2008 Feb;47(2):160-3.
5. Borman AM, Linton CJ, Miles SJ, et al. Molecular identification of pathogenic fungi. J Antimicrob Chemother. 2008 Jan;61 (Suppl. 1):7-12.
6. Ameen M, Arenas R. Developments in the management of mycetomas. Clin Exp Dermatol. 2009 Jan;34(1):1-7.

Additional Comment:

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