Dermatology Flashcards
Blastomyces dermatitidis
Blastomycosis- systemic fungal disease the primarily affects dogs, humans, and cats. It is a dimorphic fungus found in Mississippi, Missouri, and Ohio River valley, and mid-Atlantic states and Canada (Quebec, Manitoba, and Ontario). Infection occurs primarily through inhalation. This is a systemic infection that can cause damage to any organ or system including the central nervous system but the most common clinical signs and physical exam findings include: Depression, anorexia, weight loss, fever, lameness, lymphadenopathy, harsh lunch sounds, draining skin lesions, chorioretinitis, uveitis, and cough.
Definitive diagnosis depends on identification of the organism: round to ovoid yeast measuring 8-25 um. It is pale pink when stained with H & E with a refractile, double-contoured wall. They have single broad-based buds. Treat with systemic antifungal therapy, usually itraconazole.
Bullae
large blister containing serous fluid
Cheyletiella
“walking dandruff” genus of mites that live on the skin surface of dogs, cats, and rabbits
Collagenolytic granuloma (aka eosinophilic or linear granuloma)
usually occurs on the nose, chin, oral cavity, or caudal thighs. The lesions are typically raised and ulcerative or nodular.
Collarette
Characterized by a rim of peeling edges and a circular shape. Remnants fo previous primary lesions (vesicle, ballae, pustule, papule). The onset can be sudden and distribution may be widespread. Lesions are often superficial spreading pyoderma but may also be seen with some immune-mediated skin disease.
Cutaneous lupus
immune-mediated skin diseases in dogs
Cutaneous lymphoma
a disease of older dogs and cats with the most common breeds seen in our practice being Boxers and Golden Retrievers (see Photo 2). Cutaneous lymphoma can be epitheliotropic (usually T lymphocyte in origin in the dog) or non-epitheliotropic (usually B lymphocyte in origin). Sometimes referred to as mycosis fungoides, cutaneous lymphoma can have four presentations-exfoliative (see Photo 4, p. 5S) (the patient presents with erythema and a “peeling” of the skin sometimes resulting in large flakes), plaque (see Photo 5, p. 5S) (presents as nonraised, sometimes spherical shaped inflamed lesions), tumor stage (see Photos 6, 7, p. 5S) (usually varying sizes of erythemic raised, almost plateau-like lesions) and mucocutaneous ulceration/erythema.
Demodex
genus of tiny commensal mites that live in or near hair follicles of mammals
Dermatophytosis is caused by ____ and diagnosed with ____. Treatment includes:
infection of the hair, skin, or nails caused by a dermatophyte; Trichophyton, Microsporum or Epidermophyton genera. Dx with skin scraping/trichogram and identification of macroconidia. Treat with whole body therapy twice weekly (leave on lime-sulfur or eniconazole, or shampoo miconazole/chlorhex) and adjuvant local therapy (terbinafine, miconazole, ketoconazole), AND systemic antifungal therapy (itraconazole)
Eosinophilic plaques
Occur most frequently on the abdomen and medial thighs but can appear other places. They appear as single or multiple, raised, red, often ulcerated lesions of varying size (0.5-7 cm). They frequently have a cobblestone appearance and unlike eosinophilic ulcers, these are often pruritic. This condition is histopathologically similar to miliary dermatitis and is usually associated with underlying allergy.
Eosinophilic ulcer (aka indolent ulcer)
Typically occurs on the upper lip and may be unilateral or bilateral. They often have a characteristic central area of yellow to pink tissue with a slightly raised circumferential edge.
Folliculitis
Inflammation or an infection of the hair follicle
Furunculosis
Deep folliculitis resulting in a swollen, painful skin lesion
Macule
Change in surface color, without elevation or depression
Microsporum canis
Ringworm of domestic cats, also 70% of canine infections
Zoonotic. About 50% of strains fluoresce with ultraviolet light (Wood’s lamp). M. canis and M. gypseum can both present with white colony growth with a pH change at 5 to 7 days, but require different management strategies. Ultimate source of M. canis is a potentially asymptomatic cat.
Microsporum gypseum
Ringworm
Soil inhabitant - infects animals that are exposed during digging or rooting
Zoonotic
20% of canine infections
M. canis and M. gypseum can both present with white colony growth with a pH change at 5 to 7 days, but require different management strategies.
Microsporum nanum
Ringworm of pigs
Zoonotic
Mucocutaneous pyoderma
a common condition that may affect the nasal planum of dogs
Otodectes
surface mites. They are the cause of otodectic otitis, the most common mange of dogs and cats in the world. They are also found in the fox and the ferret. The mites inhabit the inner ear and feed on ear debris, they appear white in colour.
Pruritus is caused by irritation and the saliva of the mites, which is immunogenic. Secondary bacterial infection is common, resulting in purulent otitis externa which will require more treatment.
In cats, another presentation can be seen, which is that of an ectopic infection where signs are seen on other body parts such as the tail. This is due to contact e.g. cats sleeping in a curled position would allow mites to infest that area. Transmission of the mites can occur to kittens whilst they are suckling.
Papule
Circumscribed, solid elevations of skin with no visible fluid
Pemphigus foliaceus
generally a benign variety of pemphigus. It is an autoimmune skin disorder characterized by the loss of intercellular adhesion of keratinocytes in the upper parts of the epidermis (acantholysis), resulting in the formation of superficial blisters.
Pustule
small blister or pimple on the skin containing pus
Pyoderma
Term fo inflammation/infection of the skin and is often used to specifically imply bacterial skin infection, not a specific lesion.
Sarcoptes scabiei var suis
Scabies, sarcoptic mange. Main cause of mange in pigs. S scabiei var suis is highly contagious and zoonotic, though the pig is the definitive host. This parasitic mite burrows into skin causing intense pruritus and skin lesions. Tx involves avermectins at 2 week intervals for the pig. The people should go to the human doctor.
Seasonal nasal hypopigmentation
loss of pigment in the tough, hairless skin of the nose [known as the “nasal planum”] that occurs seasonally, ex. Huskey type breeds
Trichodectes
canine chewing louse, is a chewing louse found on domesticated dogs and wild canids throughout the world. host specific.
Trichophyton equinum
Ringworm
Along with T mentagrophytes main causes of ringworm in horse
Zoontic
Trichophyton mentagrophytes
Ringworm in mice and rats
Zoonotic
10% of canine infections
One of two primary causes of equine ringworm
Trichophyton verrucosum
Ringworm in cattle and horses
Zoonotic
Vesicle
small fluid-filled bladder, sac, cyst, or vacuole within the body
What is the most common etiologic agent of pyoderma in a dog?
Staph psuedintermedius (gram positive coccus)
Which mite affects clydesdale fetlocks and how is it detected?
Chorioptes; skin scraping
Paralysis of the ____ nerve can occur due to extended recumbancy and results in the inability to extend the _____
radial nerve; elbow, fetlock, carpus, digits
How can you diagnose sarcoptes?
Clinical signs (crusting in non-haired areas), Superficial skin scrape and pinnal-pedal reflex
The fur mite of rabbits is _____ and causes scaly dermatosis with areas of thinning on the dorsum
Cheyletiella
The ear mite of the horse is ____
psoroptes, psoroptic mange is reportable
Staphylococcus psuedintermedius is host-adapted to ____ whereas Staph aureus is host-adapted to _____. Playing with a dog with staph psued is ___ risk whereas playing with a dog with staph aureus is ___ risk in terms of transmission from dog to human.
Staph psued —> host adapted to dogs, low risk of transfer to human. Staph aureus —> host adapted to humans, higher risk of transmission to human (infection usually comes from person in the first place).
Collies, sheepdogs and other collie breeds are predisposed to what dermatologic disease that presents as non-pruritic dermatitis along the nose and ears?
Familial dermatomyositis; is often cyclic and will regress. Can be triggered by vaccinations, sunlight, viral infections or drugs, or sometimes no obvious cause. Dx with skin or muscle biopsy during period of clinical signs. Some cases can become severe enough to include muscle atrophy or megaesophagus
A dog presents with superficial ulceration of the nasal planum and oral mucosa, a biopsy shows residual basal keratinocytes attached to the BM with a tombstone appearance, mononuclear inflammation of the superficial dermis and IgG and complement deposition between keratinocytes. What is the diagnosis, treatment and prognosis?
Pemphigus vulgaris, 2-4mg/kg pred BID +/- azathioprine, poor long term prognosis.
What is the mechanism of pemphigus vulgaris?
IgG autoantibody binding to intracellular adhesion molecules (desmoglein) causing a loss of cohesion between keratinocytes resulting in acantholysis, vesicle formation and eventually ulceration.
What is acantholysis?
Acantholysis means loss of coherence between epidermal cells due to the breakdown of intercellular bridges.
Scaling, crusting and alopecic dermatidis around the eyes, ears, prepuce, scrotum and vulva in a siberian husky or Alaskan Malamute is suspicious for ______ related to a relative deficiency in _____
Zinc responsive dermatosis, relative deficiency in zinc
Yeast numbers greater than ___ per high power field on an ear cytology is abnormal.
> 5 / HPF
Effective treatments for uncomplicated otitis externa include what three things?
antibiotic, antifunfal and anti-inflammatory
The treatment of localized Demodex is _____ and the treatment of generalized Demodex is ____ except in ____. ____ shampoo can aid in follicular flushing.
The treatment of localized Demodex is benign neglect and the treatment of generalized Demodex is ivermectin except in heartworm positive dogs and collies/shepherds. Benzoyl peroxide shampoo can aid in follicular flushing.
Acral lick dermatitis refers to ______ and is usually secondary to ____ with a ____ component as well. Combination therapy with ______ can help break the cycle.
Acral lick dermatitis refers to chronic, repetitive licking of a region leading to trauma of the skin and is usually secondary to pruritus (allergies, neuropathy, orthopedic disease) with a behavioral component as well. Combination therapy with steroids, antibiotics, topicals, E-collar and behavioral modification/drugs can help break the cycle.
Treatment for demodex (______) can be discontinued after _____
ivermectin; two negative skin scrapings one month apart
The spot-on flea treatment for dogs, ______, is toxic to cats until it _____, because cats _____
The spot-on flea treatment for dogs, permethrin, is toxic to cats until it dries because cats lack the glucoronidation enzyme to metabolize it.
_____ is a rare, chronic, progressive and usually fatal disorder characterized by superficial necrolytic dermatitis and elevated liver values. The clinical presentation include crusting and thickening of the perioral, periocular, perineal areas and/or footpads. Histopathology shows characteristic ____ lesions.
hepatocutaneous syndrome; red white and blue lesions
How can you treat demodex mites?
Demodex is technically self limiting in dogs but antimicrobial shampoos will help prevent secondary infections. For local or generalized infections, administration of a systemic isoxazoline (afoxolaner, fluralaner, lotilaner and sarolaner) or macrocylic lactone should prevent progression. Transdermal moxidectin/imidacloprid applied weekly is effective as well. Amitraz (mitaban) is a dip labeled for generalized demodecosis. In cats, weekly lime sulfur (2%) dips or amitraz rinses are effective but labor intensive; transdermal moxidectin/imidacloprid, furalaner and sarolaner are all effective and easier to give.
How to treat sarcoptic mange in dogs?
Transdermal moxidectin and selamectin are FDA labeled for tx
In general, mites can be treated with what kinds of drugs?
macrocyclic lactones (avermectins and milbemycins), neonicotinoids (imidacloprid), lime-sulfur dips
Which are the dimorphic fungi (yeast in tissue)?
Histo, Blasto (broad base budding), coccidioidomycosis/valley fever, cryptococcus, sporothrix
Which yeast is a saprophyte (mold) in tissue?
aspergillosis
What are the four main drugs used to treat pruritus?
Apoquel (oclacitinib), Cytopoint (lokivetmab), Cyclopsorine (atopica) and steroids (prednisone)
Which cytokine mediates itch?
IL-31 via the JAK/STAT pathway
How does apoquel work?
Competitive JAK1 inhibitor
How does cytopoint work?
monoclonal antibody that binds IL-31 and prevents it from activating the JAK/STAT pathway
How does cyclosporine work?
Calcineurin inhibitor supresses cytokine IL2 which blocks proliferation of T cells
What type of hypersensitivity is atopy? What is it mediated by?
Type 1 (immediate) - IgE
A skin biopsy from an infected region showing a broad based budding organism is specific to ____ which may be associated with travel to the ____
blastomycosis; ohio river valley
