JPC SYSTEMIC PATHOLOGY
Signalment (JPC 1397818): Atlantic bottle-nosed dolphin
HISTORY: This dolphin had extensive white, crusting, cutaneous lesions.
HISTOPATHOLOGIC DESCRIPTION: Slide A: Non-haired skin: Along the epidermal-dermal junction there are multiple coalescing, expansile nodules composed of numerous epithelioid macrophages, fewer multinucleate giant cells (both Langhans and foreign body type), occasional lymphocytes, plasma cells, and rare neutrophils that separate and compress adjacent dermal collagen bundles. Extracellularly and within histiocytes and multinucleated giant cells, there are numerous round to oval, 6 - 12 µm wide, clear yeast with a 1 µm thick wall and, infrequently, a 2 - 4 µm eosinophilic center. Multifocally, the epidermis is irregularly hyperplastic, with prominent broad rete ridges. There is diffuse mild parakeratotic hyperkeratosis and multiple small colonies of 1 x 3 µm bacilli along the epidermal surface. There are colonies of mixed bacteria present within a few dermal vessels (postmortem overgrowth).
Slide B (Gridley's stain): Intrahistiocytic and extracellular 6 x 12 µm round to oval yeast are often connected by slender tubal structures forming variably long chains. Multiple yeast have single or multiple buds. Adjacent macrophages contain Gridley's positive finely granular material (digested fungi).
MORPHOLOGIC DIAGNOSIS: Non-haired skin: Dermatitis, granulomatous, nodular, multifocal, moderate, with epidermal hyperplasia, parakeratotic hyperkeratosis, and numerous intrahistiocytic and extracellular yeast, etiology consistent with Lacazia loboi, Atlantic bottlenose dolphin (Tursiops truncatus), cetacean.
ETIOLOGIC DIAGNOSIS: Cutaneous lacaziosis
CAUSE: Lacazia loboi (formerly Loboa loboi)
CONDITION: Lobo’s disease
SYNONYMS: Lobomycosis; keloidal blastomycosis
- Chronic granulomatous skin disease from yeast-like organism Lacazia loboi
- Indolent cutaneous infection with no systemic involvement
- Only rare reports of regional lymphadenopathy affecting humans and dolphins (Atlantic bottlenose dolphin and Guiana dolphin)
- Proposed to found in the environment (water, soil, or on plants)
- Phylogeny is undetermined but has been placed in the Kingdom Fungi
- Thought to follow exposure to contaminated soil or vegetation via a local penetrating injury with lesion spread via auto-inoculation
- Animals may become debilitated and die usually from secondary bacterial infections and malnutrition
TYPICAL CLINICAL FINDINGS:
- Smooth swelling progresses slowly to a nodular or verrucous, crusting white lesion
- Lesions in areas frequently exposed to the air such as top of head, dorsal fin, and top of dorsal peduncle and flukes, but may also be present on flanks and ventrum
- Occasional regional lymphadenopathy, but dissemination does not occur
TYPICAL GROSS FINDINGS:
- Multiple, elevated, nodular to verrucous, whitish, crusty lesions
- Cut surface exhibits either:
- Small, soft beige, glassy foci just beneath the epidermis
- Large circumscribed nodules extending into the deep dermis with possible ulceration of the overlying epidermis
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Histopathologic features are characteristic and diagnostic
- Large, discrete granulomas confined to the dermis with marked acanthosis, hyperkeratosis and irregular down growth of rete ridges
- Periphery of lesion commonly has foamy macrophages with PAS and Gridley's positive material believed to represent debris from digested fungi
- Yeasts stain poorly with H&E:
- Outline visible with homogenous, faintly basophilic internal contents
- 5 - 12 µm round, oval, elliptical, or crescentic (secondary to collapse of the wall)
- 1 µm thick, doubly contoured cell wall
- Budding produces chains of three or more uniform cells connected by a tubular isthmus in a characteristic 'string of pearls' pattern
- Branching chains are possible by secondary budding
- Organisms consist of a highly electron dense outer rim lining a relatively homogenous electron dense cell wall
- Organisms are often connected by a narrow, tubular portion of the cell wall
ADDITIONAL DIAGNOSTIC TESTS:
- Gridley's fungal stain
- Gomori’s Methenamine Silver
- Periodic Acid Schiff (PAS)
- Dermatitis in dolphins:
- Erysipelothrix rhusiopathiae: Gram-positive bacterium that causes a peracute septicemia with vasculitis & dermal infarcts; “diamond skin disease”
- Nocardia: Gram-positive rod bacterium, cutaneous abcessation, commonly manifests systemic dissemination
- Pox virus: Cutaneous “tattoo” lesions; solitary or coalesced circular grey blemishes with eosinophilic intracytoplasmic inclusions
- Herpesvirus (Gammaherpesvirinae): Dermatitis, proliferative genital plaque like lesions; necrotizing with eosinophilic intranuclear inclusion bodies
- Papillomavirus: Proliferative lesions on mucous membranes (frenulum, tongue, penis, vagina); metastatic spread possible
- Other fungal organism that can cause cutaneous infection :
- Histoplasma capsulatum: 2 - 4 µm intrahistiocytic yeasts with basophilic centers and peripheral clear zones
- Cryptococcus neoformans: 2 - 10 µm, spherical, yeasts with an eosinophilic center and a clear, 5 µm wide capsule
- Blastomyces dermatitidis: 15 - 20 µm broad-based budding yeasts
- Cutaneous paracoccidioidomycosis (Paracoccidioides brasiliensis): Pronounced variation in cell size and the presence of multiple blastoconidia that cover the surface of parent cells help distinguish this from loboi
- Lobomycosis only occurs naturally in humans and dolphins
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