SAM: Exam 1 dermatology

Flat Primary Lesions

• Macule: circumscribed, flat, ≤1 cm, color change, non-palpable

• Patch: macule >1 cm

Elevated Solid Primary Lesions

• Papule: sm solid elevation ≤1 cm

• Plaque: flat-topped elevation formed by coalescing papules

• Nodule: solid elevation >1 cm, extends into deeper layers

• Tumor: lg mass involving skin or SQ tissue

Elevated Fluid Filled Primary Lesions

• Pustule: sm pus-filled epidermal elevation

• Vesicle: sharply circumscribed, clear fluid-filled elevation

• Cyst: epithelium-lined cavity with fluid or solid contents

• Wheal: circumscribed, raised lesion due to edema; transient

Secondary Lesions Involving Hair

• Alopecia: hair loss, partial or complete

• Comedone: dilated follicle filled with keratin/sebum

• Follicular Casts: keratin & debris around hair shaft at follicle opening

Secondary Lesions Involving Flaking and Dryness

• Lichenification: thickened, hyperpigmented, alopecic, hyperplastic skin

• Scale: loose fragments of stratum corneum

• Crust: dried exudate on surface

• Epidermal Collarette: circular rim of scale, remnant of ruptured pustule/vesicle

Secondary Lesions Involving Skin Breaks and Loss of Continuity

• Excoriation: self-induced erosions/ulcers

• Seborrhea: dandruff

• Erosion: shallow epidermal defect, heals without scarring

• Ulcer: deeper defect exposing dermis, heals with scarring

• Fissure: linear crack through epidermis into dermis

Cytology

• Use: secondary infections, IM/neoplastic dx, therapy response 

  • Not a biopsy substitute (gold standard)

• Collection:

  • Acetate tape (#1): tape → stain → slide → dry → examine

  • Swab: external canal → roll on slide → heat fix → stain

  • Direct impression: slide pressed on lesion → dry/heat fix → stain

  • Direct pustule impression: lance pustule w/ needle → smear debris on slide

  • Dry scraping: scalpel scrape seborrhea → transfer debris → heat fix → stain

• Evaluation:

  • Normal: epithelial cells, sm # of bacti/yeast, melanin/keratohyaline granules

  • Abnormal: Inflam cells, 1> bacti/oif, > 4 yeast/oif

Skin Scraping for Dermatology

• Purpose: detect sm ectoparasites

  • Demodex, Sarcoptes, Cheyletiella

• Methods:

  • Dry scraping: scalpel scrape seborrhea → transfer debris → heat fix → stain

  • Deep skin scrape: oil skin/slide → Dull #10 blade at 45° angle until bleeding

  • Superficial skin scrape: for mites that live at surface

Hair Sampling for Dermatology

• Trichogram: Pluck hairs → mount → look for follicular casts, dermatophyte spores, parasites

• DTM: Hair pluck inoculated on medium → look for Microsporum, Trichophyton

Fine Needle Aspiration

• Use: sample deep lesions, nodules, tumors, cysts

  • distinguish inflam vs neoplastic

  • MCT, histiocytomas, lipomas, cysts

• Technique:

  • Clip, prep skin

  • 6-ml syringe + 22:20 ga needle

  • Aspirate lesion → expel on slide → smear into monolayer → air dry → stain

Cutaneous Bacteriology

• Location: Superficial epidermis & hair follicle infundibulum

• Types:

  • Resident: Multiply normally on skin

    • Dogs: Micrococcus spp, CON-staph, α-hemolytic strep, Clostridium, P acnes, Acinetobacter, COP-staph, various G- aerobes

    • Cats: Micrococcus, CON-staph, COP-staph, α-hemolytic strep, Acinetobacter

  • Transient: Present, but not significant unless pathogenic

    • Dogs: E coli, Proteus, Corynebacterium, Bacillus, Pseudomonas

    • Cats: β-hemolytic strep, E coli, Proteus, Pseudomonas, Alcaligenes, Bacillus, CON/COP staph

  • Secondary invaders: Infect damaged tissue

Pyoderma

• MOA: Cutaneous, pus-forming bacti

  • Common in dogs, rare in cats

  • Risks: Thin S. corneum, fewer lipids, higher pH, bite wound abscesses (cats)

• Class: 

  • Surface: Hot spots, intertrigo, bacti overgrowth

  • Superficial: SBF, impetigo, mucocutaneous pyoderma

    • S pseudintermedius

  • Deep: Furunculosis, cellulitis, acral lick dermatitis, interdigital nodules

Superficial bacterial folliculitis

• MOA: cutaneous, metabolic, immune, neoplasia underlying dx

  • S. pseudintermedius: Primary cutaneous pathogen

    • Very resistant: tolerates heat, dehydration, antiseptics

      • MRSP: resistance to β-lactams + FQs + Sulfas

        • Transmissible w/ active lesions, can be normal flora

  • S schleiferi: subsp Schleiferi (Coag -), subsp Coagulans (Coag +)

    • 2 types

• Cs: pustules, macule, pustule, collarettes, alopecia

• Dt: cytology (tape #1, scrape, smear), culture/cytology (poor rxn to tx)

• Tx: Topical antimicrobials (#1), systemic antibios (Tx fail in 2w, deep Dx, compliance)

  • 1st line: 1st-gen cephalosporins (cephalexin, cefadroxil), Clindamycin, Lincomycin

  • 2nd line: Cefovecin, Cefpodoxime, FQs, Doxy, Potentiated sulfonamides

    • Culture req

  • MDR: Rifampin, Amikacin, Chloramphenicol

Intertrigo

• Et: skin folds, superficial

• Cs: erythematous, macerated folds, malodor, dental dx, UTI, scooting

  • non painful/pruritic 

• Tx: weight loss, Sx excision/amputation, cleansing wipes, med shampoo, topical antibiotic 

  • Good prognosis

Impetigo

• Et: parasites, poor nutrition, dirty enviro

  • Non-contagious, superficial

• Sig: young dogs

• Cs: sm nonfollicular pustules/papules

  • not painful or pruritic, non-haired skin (inguinal/axillary)

• Tx: topical/shampoo/oral antibios (mupirocin, chlorhexidine)

Bullous Impetigo

• Et: subcorneal/intragranular pustules w/ neutrophils, acantholysis

  • Superficial, S pseudintermedius

• Sig: puppies & immunosuppressed adults 

• Cs: lg flaccid pustules, erythematous margins, collarette

  • Nonpruritic, non-follicular, groin/axillae region

Mucocutaneous Pyoderma

• Et: Staph, Superficial

• Sig: GSD
  Cs: swelling, erythema, painful/pruritic, ulceration, fissuring, depigmentation

  • lips, nose, eyelids

• Ddx: autoimmune disorders, epitheliotropic lymphoma

• Tx: oral antibiotics

  • slow response, relapses common

Pyotraumatic Dermatitis (Hot Spot)

• Et: fleas (#1), allergies, hot humid weather, thick/long coats

  • Superficial

• Cs: rapidly enlarging erythematous alopecic, weepy skin, well-demarcated, pruritic, self-inflicted

• Tx: flea control, clean, topical drying agents, antibiotics, steroids

Chin Pyoderma

• Et: granulomatous trauma response

  • Deep, Furunculosis

• Sig: Lg young short-coated dogs

• Cs: comedones, pustules, draining tracts w/ serosanguinous discharge

  • Nonpainful and nonpruritic

• Dt: cytology, skin scrap, DTM, histopath, culture

• Tx: min trauma, shampoo/topical antibios (mupirocin, peroxide)

Post-Grooming Furunculosis

• Et: contaminated grooming tools w/ Pseudomonas aeruginosa, deep infection

• Sig: Lg wired-coat dogs, <48h post grooming

• Cs: pustules, hemorrhagic fistulae, painful, fever

  • dorsal trunk 

• Dt: cytology, skin scrap, DTM, histopath, culture

• Tx: avoid contaminated grooming products

Acral Lick Granuloma

• Et: compulsive licking, deep staph infection, furunculosis

• Sig: middle-aged/older, Dobermans, Danes, Goldens, Labs, GSDs

• Cs: firm, proliferative, ulcerative alopecic lesions

• Dt: histopath, culture

• Tx: E-collar, antibios (6-8w), amitriptyline, laser ablation, topical DMSO/steroid

Canine Pedal Furunculosis

• Et: Deep infection

• Sig: short coated breeds 

• Dt: skin scrapings, cytology, biopsy, culture/sensitivity

• Tx: steroids, antibiotics, topical DMSO, cyclosporine, sx/laser removal, tetracycline, niacinamide

Malassezia

• Et: Commensal superficial yeast, inflam & hypersensitivity, immune dysfunction

  • symbiotic w/ Staph

• Types:

  • Lipid dependent: M furfur, M globosa, M restricta, M sympodialis

  • Non-lipid dependent: M pachydermatis (grow on Sabouraud’s)

• Id: Oval to peanut-shaped, thick cell wall w/ outer lamellar layer

• Sig: Basset hound, cocker spaniel, Shih Tzu, setter, Dachshund, poodle, Boxer, GSD, KCCS, summer/humid months, concurrent dermatoses

• Cs: pruritus, malodor, lichenification, hyperpigmentation, brown claws, dermatitis, black waxy otitis externa, feline acne

  • Groin, Interdigital, Ear canals, Oral cavity, Tail base

• Dt: Cytology (tape/scrape), biopsy, culture 

• Tx: topical and systemic antifungals

Antifungal medications

• Azoles: inhibit ergosterol synthesis

  • Drug interactions: Inhibition of CP450 

  • Rxn: GI upset

• Terbinafine: inhibits squalene epoxidase, ergosterol synthesis block

• Griseofulvin: fungistatic, binds microtubules + disrupts mitosis

  • works on Microsporum/Epidermophyton/Trichophyton (ringworm)

    • not effective against Malassezia

• Topicals: lime sulfur dip, miconazole, chlorhexidine

Dermatophytosis

• Et: Superficial Microsporum/Trichophyton/ Epidermophyton infection of keratinized tissue

  • M canis: most common & most zoonotic

• Epi: Zoophilic = animals, Geophilic = soil, Anthropophilic = humans  

• Cs: follicular dx, alopecia, pustule, erythema, crusts, Kerion rxn (nodules), Onychomychosis

• Dt: biopsy, PCR, dermoscopy, culture, Wood’s lamp

  • Combo tests, no gold standard 

  • M canis: white/woolly w/ yellow-orange underside

  • M gypseum: flat, suede/granular, tawny/cinnamon color

  • T mentagrophytes: white/cream powdery, underside brown/tan/red

• Tx: Systemic + topical antifungals, enviro cleaning w/ bleach/ formalin/ enilconazole

Lifestyle of parasites

• Live on the skin and feed on debris

  • Cheyletiella, biting lice 

• Live on the skin but periodically penetrate the surface for feeding

  • Fleas, sucking lice, ticks 

• Live within the skin

  • Demodex, Sarcoptes

Scabies (Sarcoptes scabiei)

• Et: contagious, not seasonal 

• Id: cup caruncle, terminal anus, unjointed pedicles

• Sig: dogs <2y, groups, rural fox contact

• Cs: papulo-crusting, “beeswax” crusts

  • elbows, hocks, periocular, ear, no haired areas

• Dt: skin scrap, cytology, trial tx, serology

• Tx: treat all, prednisone, lyme sulfur/Amitraz dips, Selamectin/Advantage Multi/Fipronil topicals, Ivermectin, Milbemycin

Notoedric Mange (Notoedres cati)

• Et: obligate parasite, contagious, cats, foxes, dogs, rabbits, humans

• Id: sm, dorsal anus, unjointed stalks 

  • look like scabies

• Cs: puritis, papules, thick skin, alopecia, gray crust

  • ears, face, eyelids, neck, feet, perineum

• Tx: treat all, Lime sulfur/amitraz dips, Ivermectin, Doramectin, Selamectin, Fipronil

Otodectes cynotis (Ear Mite)

• Et: Obligate, non-burrowing, cats, dogs, foxes, humans 

• Id: short unjointed pedicles, whip setae on hind legs (F), transverse genital opening (F)

• Cs: bilateral otitis externa, dark brown ceruminous, head shaking, scratching ears, hematomas, circling, convulsions

• Dt: direct otoscopy, microscopy

• Tx: clean ears, treat all, tresaderm drops, ivermectin, Fipronil, Selamectin, Advantage-multi

Cheyletiella (“Walking Dandruff”)

• Et: dogs (C yasguri), cats (C blakei), rabbits (C parasitovorax), humans (zoonotic)

• Id: 4 pairs of legs w/ combs (not claws), accessory mouthparts, palpi w/ hooks

• Cs: pruritus, hypersensitivity, scale, dorsal alopecia, oily coat

• Dt: superficial scrape, combing, tape preps, fecal floats

• Tx: flea control, Frontline, Revolution, Advantage-multi, lime sulfur dips, ivermectin, milbemycin

  • if Tx fails check for nasal seq

Pediculosis (Lice)

• Et: Neglect dx, host specific, direct contact, winter, obligate parasite

  • Anoplura (sucking): slow easy to find, cause anemia, irritability

  • Mallophaga (chewing): fast, hard to find, feed on debris & hair, very irritating

• Id: sm, dorsoventrally flat, wingless; claws on legs; reduced eyes

• Cs: Mousy odor, Intense pruritus, excoriations, flea bite/miliary dermatitis

  • Under hair mats, ears, body openings

• Dt: microscopic ID; tape, scrapings, combing, biopsy, nits on hair shaft

• Tx: treat all, groom, clean, pyrethrin/carbamate shampoos, 2% lime sulfur dips, ivermectin, Fipronil, imidacloprid

  • Repeat tx in 10-14d: life cycle is 12-21d

Demodicosis

• Aka: demodectic mange, follicular mange, red mange

• Et: Normal fauna, obligate parasite, live on hair folicle

  • Demodex canis, D injai (long-bodied), D cati (follicular), D gatoi (contagious, superficial, S. corneum only, cats)

• Sig: Bulldog, Shar-Pei, Pit bull, Westie, Staffordshire, Siamese/Burmese

  • juvenile demodicosis heritable → don’t breed affected dogs

• Cs: alopecia, erythema, scaling, follicular hyperkeratosis, seborrhea, pyoderma, edema, plaques, nodules, lymphadenopathy, otitis externa 

• Dx: deep skin scrapings (squeeze skin), trichography, biopsy (granulomatous)

• Tx: self limiting if mild, Amitraz, Ivermectin, Moxidectin, Milbemycin, Doramectin, Isoxazolines, lime sulfur dips, carbaryl shampoos,  Benzoyl peroxide gel 

  • Tx 4 w past 2nd negative skin scrape

  • > 50% of cases🡪 no underlying dx = reduced recovery

Hypersensitivity Reactions

• Pruritus #1 cause = allergies

• Ddx:  

  • Allergies: atopy, food hypersensitivity, flea hypersensitivity

  • Infections: bacterial, fungal

  • Parasites: fleas, scabies, demodex

  • Other: neoplasia

• Dt: IDAT (Type 1 rxn, $), serum test (no drug withdrawls)

• Tx: Immunomodulation, symptomatic therapy, avoidance

  • No cure → only control!

Atopy (Canine Atopic Dermatitis)

• Et: genetic, inflam pruritic allergic skin dx

  • IgE-mediated Type I hypersensitivity

• Sig: 6m-3y, retrievers, terriers, bulldogs, setters, shar-peis

• Cs: Puritis, flexural lichenification, Staph pyoderma, Malassezia dermatitis

  • face, ears, feet, inguinal, axilla

• Dt: rule out, CS

  • Need ≥3: Pruritus, facial/digital involvement, lichenification, chronic/relapsing dermatitis, genetics, onset <3 y, facial erythema/cheilitis, conjunctivitis, Staph pyoderma, hyperhidrosis, positive IDAT, elevated IgE/IgGd

• Tx: ASIT, Glucocorticoids, Atopica, Apoquel, Cytopoint, Zenrelia

Allergy Treatments

• Immunotherapy (ASIT): Tailored to allergens, least $ long term, few side effects, takes 6-12m for rxn

• Glucocorticoids: pred, triamcinolone, dex; immunosuppression, metabolic effects

• Cyclosporine (Atopica): Inhibits calcineurin; GI upset, ↑ ALP/ALT, ↑ cholesterol, hypoalbuminemia, UTI

• Oclacitinib (Apoquel): JAK-STAT inhibitor; vomiting, diarrhea, ↑ infections, demodicosis, neoplasia risk; Not for <12 mo, breeding, pregnant/lactating

• Lokivetmab (Cytopoint): Caninized anti-IL-31 monoclonal antibody; Blocks itch at receptor level; Monthly injection

• Ilunocitinib (Zenrelia): JAK inhibitor; Potent pruritus control; may impact vax responses, discontinue 28–90 d before/after

Food Allergy (Cutaneous Adverse Food Reaction)

• 3rd most common hypersensitivity

• Cs: gen pruritus (dogs), otitis, pyoderma, head/neck pruritus (cats), alopecia, miliary dermatitis, eosinophilic granuloma complex, plaques, pustules, ulcers, lichenification, pigment changes, GI signs, sneezing, conjunctivitis, onychitis, anaphylaxis

• Dt: food elimination diet trial + provocation for 8w (#1)

  • NEVER serum test

• Tx: Home-cooked novel protein

Flea Allergy Dermatitis

• Et: Hypersensitivity Rxn to flea saliva

  • Ctenocephalides felis felis (cat flea) most common

    • start feeding ASAP, eggs not sticky (fall off <2h)

• Sig: 3-6y; dark moist enviro, base of carpet, den of host 

• Cs: Pruritus, pustules, crusts, sm erythema on caudal dorsal half (D), miliary dermatitis (C), EGC (C) bilaterally symmetric ventral alopecia (cats)

  • Racing stripe

• Dt: leas/flea dirt, rxn to tx, IDAT

• Tx: flea collars, dips, shampoos, Adulticides (fipronil, imidacloprid, selamectin, nitenpyram, metaflumizone, dinotefuran, spinosad, pyrethrins)

Feline Atopic Skin Syndrome

• Et: allergic skin dx from enviro allergens

• Sig: Young cats 6-24m-15y

• Cs: pruritus, miliary dermatitis, self-inflicted alopecia, EGC, otitis, conjunctivitis, chronic resp dx

  •  face & neck

Eosinophilic Granuloma Complex

• Et: Group of reactive skin, mucocutaneous, and oral lesions in cats

  • Not a final diagnosis, indicates reactive pattern

• Cs: Indolent ulcer, Eosinophilic plaque and granuloma

• Tx: glucocorticoids, antibiotics, antifungals, Atopica, cryosurgery, laser, sx excision

Feline Mosquito Bite Hypersensitivity

• Et: Uncommon, seasonal, mosquitoes 

  • affects pinnae & face

• Sig: indoor, 3.3y

• Cs: Erythema, plaques, ulcers, necrosis, crusts, nodules, pigment changes, alopecia

  • Ears & face

• Tx: Keep indoors, repellents

Pemphigus Foliaceus

• Et: Viral, insects, genetic (HLA), penicillamine, phenylbutazone, UV light, chronic skin dx, stress

  • #1 intraepidermal vesiculo-pustular dx

  • Subcorneal and follicular

• Sig: 5y, DSH

• Cs: pustules, crusts, alopecia, polycyclic borders, systemic dx

  • face, ears, muzzle (#1), footpads, claws (cats), nipples

  • Bilateral, symmetrical, rapidly progressive (3-12m)

• Dt: Cytology w/ acantholytic keratinocytes in pustules, Biopsy w/ intragranular/subcorneal pustules + neutrophils/eosinophils

Pemphigus Vulgaris

• Et: Suprabasliar, DSG 3

• Cs: erosions, ulcers, pain, systemic dx

  • Oral/mucocutaneous, axillae, groin, clawbeds

• Dt: smears, biopsy, immunotesting

• Tx: pred + azathioprine (D), chlorambucil (C)

  • Poor prognosis w/o Tx

Pemphigus Erythematosus

• Et: Subcorneal: Basal cells: DSG 1

• Cs: Pustules, crusts, depigmentation, erythema, erosion

  • Face, nose

• Dt: Microscopy; acantholysis + lichenoid interface dermatitis

• Tx: glucocorticoids (pred, triam, dex)

Bullous Pemphigoid

• Dt: target hemidesmosomes @ BM for subepidermal separation from dermis

• Sig: Collies & Dobermans

• Cs: tense blisters, ulcers 

  • Oral, axillae, groin, footpad

• Dt: biopsy (subepidermal vesicles + eosinophilia), IF

  • No acanthysis 

• Tx: glucocorticoids, azathioprine, chlorambucil, tetracycline, erythromycin, avoid sun

Epidermolysis Bullosa Acquisita

• Et: Rare, subepidermal Ab to Type VII collagen

• Sig: shortly after birth

• Cs: Vesicles, bullae, erosions, ulcers

  • Footpads, oral, bony prominences

• Dt: biopsy (subepidermal clefting, min inflam), IF, EM, immunoblot, collagen VII ELISA

• Tx: symptomatic, avoid trauma, antibiotics, should not be bred

Discoid Lupus Erythematosus

• Et: UV damage, Ab keratinocyte apoptosis, Benign cutaneous or systemic form

  • #2 IM skin disease in dogs (rare in cats)

• Sig: Collies, GSDs, Shelties, Huskies, Brittany spaniels, GSPs

• Cs: depigmentation, erythema, loss of cobblestone texture, ulcers, crusting, alopecia, permanent leukoderma

  • nose, muzzle bridge, alar folds, ears

• Dt: biopsy, Immunopath (Ig, complement at BMZ)

• Tx: UV protection topical steroids, tacrolimus, cyclosporine, Vit E, EFAs, glucocorticoids

  • Good prognosis, will scar

Vasculitis

• Et: inflam of blood vessels; infections, IM dx, genetic, sun, drugs

• Sig: JRT, Scotties, GSDs, Greyhounds, Dachshunds, Rottweilers, Poodles, Silky terriers, Yorkies, Pekingese, Maltese

• Cs: Petechiae, edema, plaques, nodules, alopecia, scarring, necrosis, ulcers (“punched out”), infarcts, systemic dx

  • extremities, ear/tail tip, pressure points, paw/claws, scrotum, oral

• Dt: Lg punch/wedge biopsy 

  • neutrophilic/eosinophilic/lymphocytic perivascular inflam, fibrinoid degeneration, thrombi

• Tx: pentoxifylline, pred, cyclophosphamide, azathioprine, tetracycline/niacinamide, dapsone, sulfasalazine, Vit E

Erythema Multiforme

• Et: cell-mediated hypersensitivity

• Cs: erythema, macules, urticarial plaques, vesicles, bullae

  • Symmetrical groin, MCJ, oral, war, footpads, trunk (C)

  • Look like a target

• Dt: biopsy 

  • hydropic interface dermatitis, keratinocyte apoptosis, satellitosis of lymphocytes/macrophages

• Tx: self limiting (wks), steroids, azathioprine, cyclosporine, pentoxifylline, novel diet

Toxic Epidermal Necrolysis

• Et: keratinocyte apoptosis, drug induced 

• Cs: vesicles, bullae, necrosis, collarettes, systemic dx

  • oral mucosa, MCJ, footpads

• Dt: biopsy, CBC (neutropenia/neutrophilia), Nikolsky’s sign positive (skin shears with pressure)

• Prognosis: guarded-poor

Canine Juvenile Cellulitis (Puppy Strangles)

• Et: Sterile granulomatous derm and lymohadentis 

• Sig: puppies (3w-4m), Goldens, Dachshunds, Gordon Setters

• Cs: inflam, pustules, draining tracts, crusts, lymphadenopathy, systemic dx

  • Face, ears, joints, submandibular LN

• Dt: cytology/biopsy

• Tx: glucocorticoids

Plasma Cell Pododermatitis (Pillow Foot)

• Et: IM, FIV, food allergies

• Sig: cats; concurrent stomatitis, renal amyloidosis, glomerulonephritis

• Cs: feet w/ swollen, purplish, white striae

• Dt: biopsy (plasma cell infiltrate, Russell bodies), hypergammaglobulinemia

• Tx: doxycycline, steroids, cyclosporine, Sx

Dermatomyositis

• Et: IM dx of skin, CT, skeletal muscle

• Sig: Collies, Shelties

• Cs: pustules, vesicles, alopecia, ulcers

  • face, ears, tail, extremities, axilla/inguina

  • fatal secondary amyloidosis possible

• Dt: biopsy (follicular atrophy, perifollicular inflam), high CK/AST

  • Ddx: lupus erythematosus, nasal parakeratosis, erythema multiforme, pyoderma, pemphigus foliaceus, systemic lupus erythematosus, zinc-responsive dermatosis, vit A–responsive dermatosis, toxic epidermal necrolysis 

• Tx: pentoxifylline, predisolone

Urticaria & Angioedema

• Et: mast cell/basophil degranulation, Type I/III HS rxn

• Sig: short coat breeds 

• Cs: wheals, serpiginous arciform lesions, facial swelling

• Dt: diascopy (lesions disappear)

• Tx: remove trigger, epinephrine, glucocorticoids, antihistamines, pentoxifylline

Bacterial Pseudomycetoma (Botryomycosis)

• Et: Staph, trama, deep skin infection 

• Cs: firm nodules, draining fistulae, purulent exudate, grains (colonies)

  • Chronic, suppurative, granulomatous

• Dt: culture, biopsy (granulomatous infiltrates w/ Splendore-Hoeppli material)

• Tx: Sx excision, antibiotics (TMS, rifampin, β-lactamase resistant drugs)

Slow-growing Mycobacteria

• Et: Deep skin infection 

• ID: acid fast, takes wks to grow

• Tuberculosis: systemic dx, LN enlargement, resp/GI lesions 

  • M. tuberculosis, bovis, microti

• Feline leprosy:

  • Et + Cs + Sig: 

    • M. lepraemurium: young cats, head/limbs, painless nodules

    • M. visibile & novel: older cats,  generalized nodules

  • Dt: biopsy, histopath, PCR

  • Tx: wide Sx excision, antimicrobials

• Canine leproid granuloma:

  • Sig: Boxers, short-coated breeds, insects 

  • Cs: nodules on head

  • Tx: spontaneous, Sx excision, rifampin, doxycycline, clarithromycin

Rapid-growing Mycobacteria

• Et: Deep skin infection of M. fortuitum, M. chelonae, M. abscessus, M. smegmatis; soil, water; opportunistic, trama

• ID: acid fast, affinity for fat

• Cs: panniculitis, lobar pneumonia, disseminated dx, alopecic nodules, draining tracts, thin skin, swellings

  • Neck, shoulders, flank, dorsum

  • Not painful/pruritic 

• Dt: cytology (AFB staining), culture, biopsy

• Tx: Sx removal, clarithromycin, doxycycline, FQ, amikacin, clean w/ bleach

Actinomycosis

• Et: Opportunistic, normal oral flora, Gram+, non-acid fast, filamentous anaerobes, trama

• Cs: swelling, yellow sulfur granules, draining sinuses, malodorous exudate, pyotorax, abscess 

  • Mouth, head/neck/thorax/abdomen

• Dt: smears, biopsy, culture (Splendore-Hoeppli phenomenon)

• Tx: penicillin, clindamycin, erythromycin, rifampin, cephalosporins, Sx excision

Nocardiosis

• Et: opportunistic, Gram+, partially acid-fast, filamentous aerobes; soil saprophytes; deep skin infection 

• Sig: 2.5-11y, males

• Cs: abscesses, draining lesions, systemic illness

• Dt: culture, biopsy, CBC (anemia, leukocytosis w/ L shift, hyperproteinemia)

• Tx: sulfonamides

Eumycotic Mycetoma

• Et: Soil saprophytes, Pseudoallescheria boydii deep skin infection

• Cs: tumefaction, draining tracts, grains, solitary lesions

  • face/limbs

• Dt: biopsy/culture

• Tx: wide excision/amputation, antifungals

Phaeohyphomycosis

• Et: saprophytic pigmented fungi, soil, wounds, deep skin infection 

• Sig: GSD

• Cs: solitary nodules, ulcers

  • paw, leg, head

• Dt: biopsy, culture

  • No grains 

• Tx: Sx excision, azoles, amphotericin, cryosurgery

Hyalohyphomycosis

• Et: Non-pigmented saprophytic fungi, woulds, soil, opportunistic deep skin infection

• Sig: GSD predisposed

• Cs: Pyogranulomatous inflammation

  • Claw beds, skin, eyes, joints, lungs, kidneys, liver

• Dt: biopsy, culture

• Tx: excision, azole, amphotericin

Zygomycosis

• Et: Saprophytic spore molds, wounds, soil, deep skin infection 

  • Mucorales: Rhizopus, Mucor, Absidia, Saksenaea

  • Entomophthorales: Conidiobolus, Basidiobolus

  • Mortierellales: Mortierella

• Cs: nodules, draining ulcers, sinusitis (Conidiobolus), trunk lesions (Basidiobolus)

• Dt: biopsy (granulomatous dermatitis w/ eosinophils, hyphae)

• Tx: excision, amphotericin B, azoles, potassium iodide

Pythiosis

• Et: Pythium insidiosum deep skin infection

  • oomycete, not true fungus

• Sig: Lg-breed, young male dogs w/ outdoor, water exposure, Gulf Coast US

• Cs:

  • Cutaneous: firm boggy masses, ulceration, draining tracts, severe pruritus, self-mutilation

  • GI: vomiting, diarrhea, weight loss, segmental thickening of GI tract, mesenteric LN involvement

• Dt: cytology/biopsy (pyogranulomatous w/ eosinophils)

• Tx: Sx excision/amputation (#1)

  • antifungals ineffective

Lagenidiosis

• Et: Oomycete deep skin infection

• Sig: SE US, water-associated

• Cs: multifocal nodules, draining tracts, systemic vasculitis

  • great vessels, LN, lungs, mediastinum

• Dt: biopsy, culture, PCR

• Tx: amputation

  • Grave prognosis if systemic

Cryptococcosis

• Et: C. neoformans deep skin infection, yeast-like, inhalation pigeon dropping

• Sig: Siamese, young Lg dogs

• Cs: polyps, ulcers, abscess, upper resp dx, neuro/ocular signs, CNS dx

  • Nose, ears, paws

• Dt: cytology (narrow-based budding yeast w/ capsule halo), latex agg (capsular antigen), biopsy (mucicarmine stain)

• Tx: azoles, amphotericin B, flucytosine, Sx

Otitis

• Et: bacti infection, Malassezia yeast, drug eruption, over-cleaning, FB, allergies, IM dx, metabolic dx

  • OM: Pseudomonas aeruginosa, S. pseudintermedius 

• Cs: malodor, head shaking, scratching, aural hematoma, hearing loss, behavior changes, pinnal alopecia

• PE: Nose parallel to ventral, hand behind head, Pull pinnae towards you and rotate down

• Dt: Cytology (OE), Culture (OM), biopsy, imaging, myringotomy

• Tx: Ear cleaning, steroids, thiabendazole, dex, neomycin, NeoPolyB-HC, Miconazole, Tris-EDTA combos, hydrocortisone aceponate, miconazole, gentamicin, osurnia (OE)

Sebaceous Adenitis

• Et: inflam disorder of sebaceous glands

• Sig: Poodle, Akita, Vizsla, Samoyed, Chow, young adult to middle-aged

• Cs: scaling, follicular casts, dry broken hairs (brown/red), nodular alopecia, fine white scaling, “Moth-eaten” alopecia

  • Bilateral symmetric, head, ears, dorsal trunk, tail, legs

• Dt: Histopath

  • acanthosis, hyperkeratosis, follicular plugging, keratin sheathing hairs, absent sebaceous glands, granulomatous  perifollicular inflam

• Tx: Spontaneous, keratolytic shampoos, emollient/oil/ propylene glycol rinses, FA supplements, synthetic retinoids, cyclosporine, tetracycline, niacinamide

Hyperkeratose

• Idiopathic Nasodigital Hyperkeratosis

  • Et: Senile change

  • Cs: hyperplastic keratin, verrucous ridges, splitting, margin debris

    • nasal planum & paw pads

• Familial Footpad Hyperkeratosis

  • Sig: Irish Terriers, Dogue de Bordeaux, <6m

  • Cs: all pads affected, horn formation, lameness

• Nasal Hyperkeratosis

  • Sig: 6-12m, Labs

  • Cs: Dry, rough, gray/brown keratin accumulation, fissures, loss of cobblestone texture, hypopigmentation

• Tx: Soaking, Petroleum jelly, propylene glycol, tretinoin gel, Douxo spot-on, Bag Balm, Trim growths, Vit A, tacrolimus, topical steroids

Epidermolytic ichthyosis

• Et: Prime disorders of Cornification, keratin 10 mutation

• Sig: Norfolk Terriers

• Cs: cobblestoned hyperpigmented scaling, discolouration, ear scaling,  Erythema, keratinous debris, Alopecia, Lichenification,

  • at birth

• Dt: Vacuoles and lysis of KC in spinous and granular cell layers, hypergranulosis, hyperkeratosis

• Tx: salicylic acid, sulfur, tar, selenium sulfide, Emollients, moisturizers, humectants

Breed Specific ichthyosis

• Et:

  • Golden Retriever ichthyosis: Prime disorders of Cornification, PNPLA1 mutation

  • Bulldog ichthyosis: Prime disorders of Cornification, NIPAL-4 mutation

• Cs: Erythema, keratinous debris, Alopecia, Lichenification, hyperpigmentation

• Tx: salicylic acid, sulfur, tar, selenium sulfide, Emollients, moisturizers, humectants

Psoriasiform-Lichenoid Dermatosis

• Et: Prime disorders of Cornification

  • Staph worsens dx

• Sig: Cockers, Labs, Schnauzers, Setters; hyperkeratotic plaques, follicular casts

• Cs: Erythema, keratinous debris, yellow plaques, Alopecia, Lichenification, hyperpigmentation

  • Non puritic, asymptomatic, symmetric 

• Tx: cephalexin

Schnauzer Comedo Syndrome

• Et: genetic, disorders of Cornification

• Sig: min schnauzers 

• Cs: Erythema, keratinous debris, Alopecia, Lichenification, hyperpigmentation

• Tx: acne cleaning pads, alcohol, listerine, sulfur, tar, Benzoyl peroxide

JRT Ichthyosis

• Et: Nonepidermolytic Ichthyosis, disorders of Cornification, TGM1

• Cs: Large, thick, adherent, parchment paper-like scales

• Tx: salicylic acid, sulfur, tar, selenium sulfide, Emollients, moisturizers, humectants

Zinc-Responsive Dermatosis

• Et: Disorders of Cornification

  • Syndrome I: Huskies, Malamutes 

  • Syndrome II: puppies on poor diets (excess Ca, phytates inhibit Zn absorption)

• Cs: erythema, alopecia, scaling, facial crusting, dull coat, greasy skin, footpad hyperkeratosis, poor smell/taste

• Dt: biopsy (parakeratotic hyperkeratosis, papillomatosis, spongiosis)

• Tx: correct diet, zinc supp, treat infections

Superficial Necrolytic Dermatitis

• AKA: Necrolytic migratory erythema, hepatocutaneous syndrome, metabolic epidermal necrolysis

• Et: nutritional imbalance (hypoaminoacidemia) due to hyperglucagonemia, liver dysfunction

• Sig: older dogs

• Cs: PU/PD, crusted erosions/ulcers, high liver enzymes,  hyperglycemia

  • muzzle, mucocutaneous junctions, distal limbs, pawpads

• Dt: “red, white, blue” pattern (parakeratotic hyperkeratosis + keratinocyte vacuolation + basal hyperplasia)

• Tx: amino acid supplementation

  • poor prognosis

Canine Cosmetic Pattern Baldness

• Ventral-Type Alopecia (#1)

  • Sig: Dachshund, Chihuahua, MinPin, Whippet, Greyhound, Italian Greyhound, Terriers, Boxer, 6m

  • Cs: Symmetrical, progressive, ventral neck, chest, abdomen, caudomedial thighs, perineum, postauricular regions

    • Normal coat at birth

• Pinnal Alopecia

  • Sig: Dachshund, Chihuahua, Boston Terrier, Whippet, Italian Greyhound, <1y

  • Dt: biopsy (in anagen, reduced size/diameter of air folicle)

  • Tx: none, melatonin trialed

• Injection Reactions

  • Et: 2-4 months post-injection, rabies vax (inflam), steroid injection (non inflam)

  • Cs: erythematous firm plaque, SQ swelling,  alopecia, hyperpigmentation, shiny skin

    • shoulders, back, posterolateral thighs

  • Dt: biopsy (panniculitis, dermal/pilosebaceous atrophy)

  • Tx: none, excision, Intralesional/systemic GC, pentoxifylline, dapsone

• Post-Clipping Alopecia

  • Et: failure of hair regrowth post-clipping (follicular arrest)

  • Sig: long/thick coats; Siberian Husky, Chow

  • Tx: regrows after heavy shedding

• Recurrent Flank Alopecia

  • Et: seasonal follicular dysplasia; fall/winter, photoperiod, genetics

  • Sig: Boxers, Bulldogs, Airedales, Schnauzers, Poodles, Frenchies

  • Cs: well-demarcated alopecia, hyperpigmentation, scaling, folliculitis

    • Symmetric, Sporadic, bon-pruritic, non-inflamed,

  • Dt: biopsy (dysplastic/atrophic, keratin-filled follicles w/ finger-like projections)

  • Tx: regrowth in 3-8m, melatonin

Canine Metabolic Pattern Baldness

• Hypothyroidism

  • Et: decreased T4 & T3 production

  • Sig: Beagles, Dobermans, Setters, Ridgebacks, Giant Schnauzers, Deerhounds, Boxers, GSD, middle-aged, neutered/spayed dogs

  • Cs: symmetric alopecia, rat tail, brittle coat, hyperpigmentation, pyoderma, OE, seborrhea, facial myxedema, lethargy, mental dullness, weight gain, cold intolerance, exercise intolerance, anorexia

  • Dt: low tT4 + fT4, high TSH, high ALT/ALP, fasting hypertriglyceridemia, hypercholesterolemia

  • Tx: sodium L-thyroxine

• Hyperadrenocorticism (Cushing’s Disease)

  • Et: excessive cortisol

  • Sig:

    • PDH: Sm breeds, middle-aged

    • ADH: Lg breeds, ⅔ female

  • Dt: endocrine testing

  • Cs: PU/PD, lethargy, weakness, pot belly, panting, neuro signs, stiff gait, alopecia, thin skin, bruising, comedones, hair color changes, vein dilation, hyperpigmentation, poor wound healing

Idiopathic Sterile Granuloma/Pyogranuloma

• Sig: Collies, Weimaraners, Great Danes, Boxers, Goldens

• Cs: Firm, painless, papules, nodules, alopecic, ulcerated lesions, orange-yellow friable plaques

  • Wax/wane, regress spontaneously, non pruritic

  • muzzle, periocular, pinnae, paws

• Dt: No organisms on cytology/culture, biopsy (diffuse granulomatous dermatitis)

• Tx: excision, glucocorticoids, tetracycline, niacinamide, azathioprine, cyclosporine, spontaneous

Systemic Antimicrobials

• β-Lactams: HS, GI upset; synergistic w/ aminoglycosides, cephalosporins, polymyxin; antagonism w/ tetracycline/chloramphenicon; avoid w/ allopurinol as drug eruption risk in people

• Macrolides: GI upset, hepatomegaly, cholestatic hepatitis, high liver enzymes

  • azithromycin, clarithromycin, erythromycin, tylosin

• Lincosamides (Clindamycin): mild GI upset

• Chloramphenicol: blood dyscrasias, BM suppression, aplastic anemia, GI upset, contradicted in liver dysfunction

• Aminoglycosides: nephrotoxicity, ototoxicity, vestibulotoxicity, placental transfer

• Tetracyclines: stained teeth, enamel hypoplasia, impaired bone growth, GI/hepatic toxicity, nephrotoxicity, esophageal strictures

  • Doxycycline, Minocycline

• Fluoroquinolones: GI upset, neurotoxicity, arthropathy

  • enrofloxacin, marbofloxacin, ciprofloxacin

• Sulfonamides: HS, hepatotoxicity, aplastic anemia, thrombocytopenia, neutropenia, crystalluria, KCS, thyroid suppression

• Rifampin: High liver enzymes, rash, BM effects, GI upset, orange-colored urine/tears/sweat/saliva

Topical Therapy

• Antipruritics: symptomatic therapy; mediator removal, counter-sensations (hot/cold), nerve blockade, moisturizing barrier, GC use

  • 1% hydrocortisone, 0.01% fluocinolone, 2% diphenhydramine, 1% pramoxine

• Emollients/Moisturizers: soften/lubricate skin, after hydration; hypoallergenic shampoos

  • fatty acids, lipids, urea, glycerin, colloidal oatmeal, chitosanide

• Antibacterials

  • Chlorhexidine: antiseptic, yeast activity

  • Benzoyl Peroxide: antibacterial, keratolytic, follicular flushing, degreasing, anti-pruritic

  • Ethyl lactate: mild, degreasing, comedolytic, less drying than BPO

• Antimycotics

  • azoles, chlorhexidine: antifungal

  • Sulfur: antifungal, antibacterial, antiparasitic, degreasing; cheap/nontoxic; bad odor, stains, cats need e-collar until dry