JPC SYSTEMIC PATHOLOGY

INTEGUMENTARY SYSTEM

September 2016

I-F13 (NP)

Signalment (JPC 2749408):  Female baboon (Papio spp.)

HISTORY:  This baboon had multiple, raised, firm, often ulcerated skin nodules on the face, hands, feet, and tail areas.  The lesions recurred following surgical removal and did not respond to medical therapy.

HISTOPATHOLOGIC DESCRIPTION:  Haired skin:  Expanding the dermis and subcutis, compressing adnexa, and elevating or abutting the overlying moderately hyperplastic and focally ulcerated epidermis, are multifocal to coalescing nodular infiltrates composed of high numbers of epithelioid macrophages and multinucleated giant cells (Langhans type) containing numerous round to ovoid, pale eosinophilic 8-15um diameter yeast, with a 2-3um thick wall, single, narrow-based buds, and a single, 2um diameter round, peripheral nucleus. Within these areas are viable and degenerate neutrophils, cellular debris (lytic necrosis), fewer lymphocytes and low numbers of plasma cells and eosinophils and scattered areas of hemorrhage. There is diffuse acanthosis, orthokeratotic hyperkeratosis, and spongiosis.  There is focal ulceration covered by a serocellular crust composed of necrotic and keratin debris, hemorrhage, and many yeast.

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Dermatitis, pyogranulomatous, eosinophilic, nodular, multifocal and coalescing, moderate, with numerous intrahistiocytic yeast, ulceration, epidermal hyperplasia, and hemorrhage, baboon (Papio spp.), nonhuman primate.

ETIOLOGIC DIAGNOSIS:  Cutaneous histoplasmosis

CAUSE:  Histoplasma capsulatum var. duboisii

CONDITION:  African histoplasmosis

SYNONYMS:  Large-form histoplasmosis

GENERAL DISCUSSION: 

PATHOGENESIS: 

TYPICAL CLINICAL FINDINGS: 

TYPICAL GROSS FINDINGS: 

TYPICAL LIGHT MICROSCOPIC FINDINGS: 

 ULTRASTRUCTURAL FINDINGS:

 ADDITIONAL DIAGNOSTIC TESTS: 

 DIFFERENTIAL DIAGNOSIS:  (Histological lesions) 

Organism

Histoplasma capsulatum

var. duboisii

Histoplasma capsulatum

var. capsulatum

Cryptococcus neoformans

Coccidioides immitis

Blastomyces dermatiditis

Tissue response

Pyogranulomatous with MNGC

Histiocytic

Histiocytic, min. to mod.

Pyogranulomatous

Pyogranulomatous

Size (μm)

8-15

2-4

2-10

5-100

8-15

Cell wall thickness

Thick

Thin

Thin

Thick

Thick

Number of nuclei

Single

Single

Single

None

Multiple

Bud and attachment

Single bud; narrow-based

Single bud; narrow-based

Single bud; narrow-based

None

Single bud;

broad-based

Capsule

None

None

Mucicarmine-positive

None

None

Endospores

None

None

None

Yes

None

Dimorphic

Yes

Yes

Yes

Yes

Yes

Common species affected

Baboons

Humans

Dogs

Cats

Cats

Many species

Dogs

Common sites affected

Skin

Bone

Lung

Disseminated

Lung

CNS

Lung

Lung

Skin

Disseminated

Modified from Migaki G, et. al., 1993

COMPARATIVE PATHOLOGY: 

REFERENCES: 

  1. Gades NM, Marler RJ. Pathology in Practice. J Am Vet Med Assoc. 2009;234(12):1535-7.
  2. Simmons J, Gibson SV. Bacterial and mycotic diseases. In: Bennett BT, Abee CR, and Henrickson R. Nonhuman Primates in Biomedical Research: Diseases. 2nd ed. London, UK: Academic Press; 2012:153
  3. Migaki G, Hubbard GB, Butler TM. Histoplasma capsulatum duboisii infection, baboon. In: Jones TC, Mohr U, Hunt: Nonhuman Primates II: Monographs on Pathology of Laboratory Animals. New York, NY: Springer-Verlag; 1993:19-23


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