Lobomycosis Workup

Updated: Apr 14, 2017
  • Author: Manuel Valdebran, MD; Chief Editor: Dirk M Elston, MD  more...
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Workup

Laboratory Studies

Laboratory studies are not required.

Lesions can be gently scraped with a sterile scalpel blade and placed on a microscope slide with a coverslip with or without the use of 10% potassium hydroxide (KOH) or the use of a calcofluor preparation of strips of vinyl adhesive tape may demonstrate the yeast. [43, 48, 69]

An experimental research technique has been developed to determine the viability of L loboi to gauge success of therapy. The method uses fluorescein diacetate-ethidium bromide (FD-EB) vital staining and appears to be reliably sensitive and specific for viability determination of L loboi. [70]

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Imaging Studies

Imaging studies are not required.

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Other Tests

Other tests are not required.

Miranda and Silva have used vinyl adhesive tape (Scotch test) and direct microscopy to diagnose lobomycosis. This method presumably is possible because of transepidermal elimination of infectious organisms. [43] This test is an attractive, noninvasive, and inexpensive novel technique to diagnose L loboi infection, but additional research is needed to validate the method.

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Procedures

Findings on skin biopsy are diagnostic.

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Histologic Findings

Histologic examination reveals a granuloma with mostly histiocytes, multinucleated giant cells (average of 10 nuclei), asteroid bodies (ABs), and numerous fungal cells lined up in rows like a child's pop beads. [13, 67, 71] The identified inflammatory cells in a granuloma show the following frequency: CD68+ histiocytes > CD3+ T lymphocytes > CD4+ T lymphocytes > CB8+ T lymphocytes > CD57+ natural-killer cells > CD79+ plasma cells > CD20+ B lymphocytes. [67]

Granulomas are limited in distribution to the dermis, [56] and a delicate layer of collagen may separate the granuloma from the epidermis. [72] The epidermis can be normal, atrophic, or it may have pseudoepitheliomatous hyperplasia, [72] or its papillae may be short. [56]

Xanthomized histiocytes with clear or finely granular eosinophilic cytoplasm occasionally may be seen. [42]

Necrosis is rarely present. [46] Fungal cells are abundant in the macrophages. [19] The fungal cells are highlighted with Gomori Methenamine silver and periodic acid-Schiff stains. [48] Lymphocytes, plasma cells, and leukocytes are found in small numbers. [13] No nerve infiltration is present, and blood and lymphatic vessels are normal. [13]

The presence of intracellular ABs has been described in infiltrating giant cells in granulomatous conditions, including lobomycosis. These ABs have been confused with similar-appearing structures in pathologic specimens obtained from patients with sporotrichosis. Whereas ABs of sporotrichosis consist of a central yeast surrounded by eosinophilic spicules, ABs of lobomycosis are intracellular filamentous structures that contain lipid myelin figures. [73, 74]

See the image below.

Characteristic histologic appearance of the organi Characteristic histologic appearance of the organism. Courtesy of Dr Roberto Baruzzi, Sao Paulo, Brazil.

 

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