JPC SYSTEMIC PATHOLOGY
Signalment (JPC# 1629462): Four-year-old, female, rhesus monkey (Macaca mulatta)
HISTORY: Nodular lesions were present in the subcutaneous tissues near the right scapula and within the pharynx.
SLIDE A: Haired Skin: Expanding the dermis and subcutis, elevating the mildly acanthotic, multifocally ulcerated epidermis and extending to one surgical margin is a well-demarcated, thinly encapsulated, 1 x 3 cm nodule composed of predominantly multinucleated giant cells admixed with moderate numbers of reactive fibroblasts. Multinucleated giant cells are primarily Langhans type, with occasional foreign-body type, and contain up to 20 nuclei. Multifocally, multinucleated giant cells surround variably sized foci of large foamy epithelioid macrophages. Multifocally surrounding smaller caliber subcuticular and dermal vessels there are accumulations of numerous lymphocytes, scattered plasma cells, neutrophils, and eosinophils. Rarely within the giant cell cytoplasm, there are 2‑4 um wide, parallel, thick-walled, septate hyphae with non-dichotomous branching, and 8‑12 um diameter yeast. Overlying the ulcerated dermis is a serocellular crust composed of necrotic debris, degenerate neutrophils, and fibrin.
SLIDE B: Haired skin (PAS): Multinucleated giant cells contain variable numbers of PAS positive, 2-4 um diameter, parallel, thick-walled, septate hyphae with non-dichotomous branching and occasional bulbous swellings. Multifocally there are irregularly round, 8-12 um diameter spheres with blue central 3-7 um cores surrounded by a clear halo (yeast).
MORPHOLOGIC DIAGNOSIS: Haired skin: Dermatitis, granulomatous, nodular, focally extensive, moderate, with ulceration, and many intrahistiocytic fungal hyphae and yeast, rhesus monkey (Macaca mulatta), nonhuman primate.
ETIOLOGIC DIAGNOSIS: Dermal paecilomycosis
CAUSE: Paecilomyces sp.
CONDITION: Cutaneous hyalohyphomycosis (paecilomycosis)
- Ubiquitous saprophytic fungi found in soil and decaying organic matter
- Disease is extremely rare
- Hyalohyphomycosis is both subcutaneous and systemic, caused by non-pigmented, non-dematiaceous fungi
- Causes of hyalohyphomycosis (paecilomycosis) include Paecilomyces, Pseudoallescheria, Geotrichum, Acremonium, and Fusarium
- Opportunistic infection via entry into a cutaneous wound or ear canal
- Wide dissemination to include:
- Pneumonia (dogs, horses, reptiles)
- Keratitis (horses) and chorioretinitis (dogs)
- Discospondylitis (dogs)
TYPICAL CLINICAL FINDINGS:
- Lethargy, weight loss, diarrhea, chorioretinitis
- Signs associated with infection of the central nervous system: deafness, ataxia, vestibular signs, seizures
TYPICAL GROSS FINDINGS:
- Cutaneous nodule, +/- ulceration of overlying epidermis, non-healing abscess, draining fistulous tracts
- Focal or generalized lymphadenopathy
- Disseminated infection, diskospondylitis, chorioretinitis, keratitis
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Nodular to diffuse granulomatous to pyogranulomatous inflammation
- Abundant multinucleate giant cells; Langhans and foreign body type, large foamy macrophages
- Thick-walled, regularly septate, nondichotomous branching, hyphae with sporadic bulbous dilations
- Large and small (2-15um) eosinophilic ellipsoid yeast forms with broad based budding
ADDITIONAL DIAGNOSTIC TESTS:
- GMS, PAS
- Other mycotic granuloma: Sporothrix, Blastomyces, Mycobacterium, Cryptococcus, phaeohyphomycosis (Alternaria, Drechslera, Exophiala, Philophora spp.)
- Other granulomatous diseases including foreign body reaction, sterile granuloma, pyogranuloma syndrome
- Cutaneous neoplasia
- Diseases causing a generalized lymphadenopathy: Lymphoma, ehrlichiosis, Toxoplasma
- Described in dogs, cats, guinea pigs, horses, various reptiles, and humans
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