Abstract
Image 1
A. Hyperadrenocorticism
Calcinosis cutis is a cutaneous manifestation of hyperadrenocorticism (Cushing’s disease) in dogs, especially of the iatrogenic form. It usually occurs along the dorsum, axilla, or inguinal region. Mineral deposition, highlighted by Von Kossa staining (Image 1), may occur in the dermis, subcutis, or epidermis. Less common causes include percutaneous absorption of calcium-containing compounds, renal insufficiency, idiopathic, and severe systemic disease in puppies. The cause in this case is not known. Other changes that can occur with hyperadrenocorticism are follicular atrophy, increased kenogen (hairless telogen) follicles and, less commonly, follicular keratosis and atrophy of the epidermis, dermis, and sebaceous glands.
Additional reading: Doerr KA, Outerbridge CA, White SD, et al. Calcinosis cutis in dogs: histopathological and clinical analysis of 46 cases. Vet Dermatol. 2013;
Contributor: Abbie Metcalfe, University of Tennessee, Knoxville, TN
Image 2
D. Photosensitivity
Photosensitization is a light-induced dermatitis caused by heightened sensitivity of nonpigmented, sparsely haired areas of the skin to sunlight. Hepatogenous (secondary) photosensitization is caused by an increase of circulating phylloerythrin, a photoreactive metabolite of chlorophyll that is normally detoxified in the liver. Many horses do not develop photosensitivity until cirrhosis of the liver occurs. Usually, chronic liver damage is due to hepatotoxic plant ingestion. Plant-induced hepatopathy generally results in bridging portal fibrosis (Image 2; trichrome stain) with hepatocellular necrosis, biliary proliferation, and megalocytosis. The other conditions would not exclusively affect the non-pigmented skin.
Additional reading: Stegelmeier BL. Equine photosensitization. Clin Tech Equine Pract. 2002;
Contributor: Helen Jones, University of Georgia, Athens, GA
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D. Staphylococcus xylosus
Scaly skin disease is a condition in mice commonly caused by Corynebacterium bovis, a lipophilic bacterium with tropism for keratin. The clinical disease is typically associated with both immunodeficiency and hairlessness, as with nude mice. It causes diffuse scaling dermatitis grossly and orthokeratotic hyperkeratosis and epidermal hyperplasia with gram-positive coryneform rods and minimal to absent inflammation histologically. Staphylococcus xylosus (this case) causes a similar syndrome but incites epidermal ulceration and prominent inflammation (Image 3). Pseudomonas aeruginosa causes conjunctivitis and subcutaneous edema around the head. Corynebacterium kutscheri causes abscesses in the liver, kidney, and lungs (pseudo-tuberculosis). Rodentibacter pneumotropicus causes inflammation of the eye and adnexa and the ear canal.
Additional reading: Barthold SW, Griffey SM, Percy DH. Mouse. In: Barthold SW, Griffey SM, Percy DH, eds. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: Blackwell Publishing; 2016:67–71.
Contributor: Kevin O’Brien, University Laboratory Animal Resources, University of Pennsylvania, Philadelphia, PA
Image 4
A. Dermatophilus congolensis
Dermatophilus congolensis causes dermatitis in young and immunocompromised horses, as well as in those chronically exposed to wet conditions. The prolonged moisture activates and facilitates the spread of zoospores to the animal skin, where they germinate into filaments and attract neutrophils that separate the infected epidermis from the dermis, creating alternating layers of orthokeratotic or parakeratotic hyperkeratosis and neutrophils with necrotic cell debris (Image 4). The bacteria form long branching filaments of parallel rows of cocci that resemble train tracks within the skin crusts or hair follicles. None of the other organisms listed form filaments with this appearance.
Additional reading: Mauldin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy & Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. St Louis, MO: Elsevier; 2016:632–634.
Contributor: Valentina Stevenson, Virginia-Maryland College of Veterinary Medicine, Blacksburg, VA
Veterinary Pathology invites submission of exceptional gross or microscopic images for consideration as an Image Challenge, along with a multiple-choice question and answer. For details, see the Instructions to Authors on the journal website.
