Dermatology Online Journal

Cutaneous myiasis arising in an eccrine adnexal neoplasm.
Sherrif F Ibrahim MD PhD¹, Jennifer Pryor MD², Richard W Merritt PhD³, Glynis Scott MD^1,2, and Lisa A Beck MD¹
Dermatology Online Journal 14 (6): 6

1. Department of Dermatology, University of Rochester Medical Center, Rochester, New York. sherrif_ibrahim@urmc.rochester.edu
2. Department of Pathology, University of Rochester Medical Center, Rochester, New York
3. Department of Entomology, Michigan State University, East Lansing, Michigan

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Abstract

Myiasis is the infestation of human tissue by fly maggots. Although it is most often reported in tropical and sub-tropical regions of the world and in travelers returning from these areas, cases do occur in the United States. We report here a case of cutaneous myiasis observed in the setting of an eccrine adnexal neoplasm in an otherwise healthy host. Entomological analysis of the isolated organisms revealed additional information of interest.

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Introduction

Myiasis is defined as an infestation of the organs and/or tissues of man and other animals by fly maggots belonging to the order Diptera [1]. Several species of larvae that normally breed in meat or carrion may become involved in cutaneous myiasis. Although it is most often reported in tropical and sub-tropical regions of the world and in travelers returning from these areas [2], cases do occur in North America. The few reported cases contracted in North America have been largely limited to hospitalized or chronically ill patients and are caused by noninvasive blowflies laying eggs in preexisting wounds [3]. We report here a case of cutaneous myiasis observed in the setting of an eccrine adnexal neoplasm in an otherwise healthy host.

Case Report

A 51-year-old man presented to the Department of Dermatology at the University of Rochester Medical Center with the chief complaint that his "birthmark was bleeding." Upon further questioning, the patient recalled that he had a lesion on the scalp for as long as he could remember and that it had been growing in size recently, but was otherwise asymptomatic. He was employed in the stockroom of a warehouse and his boss noticed sanguineous drainage from the patient's scalp; the boss requested that the patient seek medical care. The patient had never traveled outside of the Western New York area and had no history of chronic disease.

Figure 1a	Figure 1b
Figure 1. Gross and microscopic findings of myiasis. (a) Gross image of scalp lesion. Histological examination at 40 (b), and 400X (c) with hematoxylin and eosin stain demonstrates lobules of basaloid cells in a jigsaw puzzle pattern within the dermis. Areas of the tumor are less differentiated, showing a more glandular growth pattern with extensive necrosis. Immunocytochemical stains were strongly positive for cytokeratin 7, consistent with eccrine origin.

Figure 1c

The punch biopsies demonstrated findings consistent with eccrine spiradenoma with some areas suggestive of a low-grade adnexal carcinoma (Figs. 1b-1c).

Because histology was suspicious for malignancy, full excision was indicated. The patient failed to present for his follow-up appointment and had provided inaccurate contact information. Despite numerous efforts to reach him, he was lost to follow-up.

Upon physical exam, the patient was in no apparent distress. Skin examination was notable for a 5.5 cm round tumor with central ulceration and multiple small puncta (Fig. 1a). Upon manipulation of the tumor, a single larva emerged from each opening. The tumor was anesthetic; debridement of its superficial aspect and removal of approximately 12 larvae elicited neither pain nor discomfort. Punch biopsies from 3 regions were obtained for histological analysis. After further debridement, the patient was treated with a course of cephalexin as empiric therapy for bacterial superinfection and sent home with instructions to follow-up once biopsy results had returned.

Figure 2a	Figure 2b
Figure 2. Isolated larvae. (a) Approximately 12 larvae were isolated from the patient's scalp; (b) Microscopic image showing spiracles at the terminal end of the larvae that need to be exposed to the outside for breathing. The photo was taken using a Nikon COOLPIX 5000 digital camera under an OLYMPUS SZX12 scope with an approximate total magnification of 16x (Photo by R. Kolar); (c) Lateral view of larva belonging to the family Sarcophagidae, genus Sarcophaga sp.

Figure 2c

Larval specimens were fixed in formalin and sent to the Department of Entomology at Michigan State University for identification (Fig. 2). They were identified as members of the family Sarcophagidae or flesh flies belonging to the genus Sarcophaga sp. Further identification to species level was not possible without examining an adult fly. Unlike the blow flies (Calliphoridae) that deposit eggs, the flesh flies are ovoviviparous, which means that the female gives birth to a limited number of large and relatively active larvae. The adults of these flies are attracted to carrion and excrement under most conditions. The females normally enter dwellings to deposit their larvae, which are frequently found on human corpses located indoors [4]. Based on the size (6-8 mm in length) and stage of these larvae (3rd instars), it was determined that they had colonized the patient's tumor approximately 3-4 days previous to the time of collection.

This case of cutaneous myiasis is unusual in that the patient had never traveled to endemic areas; he was neither recently hospitalized nor otherwise chronically ill. Furthermore, the majority of North American cases of myiasis have occurred with larvae from the family Calliphoridae or blowflies. In a study of 42 cases of US-acquired myiases, the most common species found in wounds was P. sericata (green blowfly), isolated from 71 percent of the patients; flesh flies were only reported in 4 cases [3].

In the United States, there have been a handful of cases of cutaneous myiasis developing in skin tumors. These tumors have tended to be neglected and allowed to progress without medical attention for prolonged periods [5]. Although myiasis contracted abroad is characteristically of the furuncular type (resembling a furuncle with a single larva contained), those cases in skin tumors are predominantly of the wound type (containing several larvae). The duration of this patient's skin tumor is unclear. However, given the history of the tumor's presence since birth, it is possible that this represented a nevus sebaceous that underwent malignant transformation or necrosis, providing a favorable environment for larval infestation.

References

1. James, M. T. The flies that cause myiasis in man. U. S. Dept. Agric., Misc. Publ. No. 631. 1947.

2. Ryan ET, Wilson ME, Kain KC. Illness after international travel. NEJM. 2002;347:505-516. PubMed

3. Sherman, R. A.Wound myiasis in urban and suburban United States. Arch. Intern. Med. 2000;160:2004-2008. PubMed

4. Byrd, J. H. and J. L. Castner. Forensic entomology: The utility of arthropods in legal investigations. 2001; CRC Press, Boca Raton, FL 417 p.

5. Hawayek LH and Mutasim DF. Myiasis in a giant cell squamous cell carcinoma. JAAD. 2006;54:740-741. PubMed

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