Scaling Flashcards
describe scales vs crusts
scales/dandruff/flakes: excessive accumulation of stratum corneum that does not exfoliate in normal fashion
-scales correspond to clusters of corneocytes
crusts/scabs: composed of corneocytes, fibrin, and blood cells
-external covers of underlying erosions or ulcerations
are scales usually a primary or a secondary lesion?
> 90% of scale cases have an underlying disease that results in secondary scale production!
-almost every skin disease can be accompanied by scaling due to inflammation that stimulates epidermis turnover
-primary cornification disorders are rare and are due to genetic epidermal abnormalities that result in abnormal cornification (NOT primary keratinization diseases)
describe ichthyoses (primary cornification disorders)
- very rare diseases; juvenile onset scaling is due to a genetic disorder of the epidermis
- autosomal recessive congenital ichthyosis: type 1
-most commonly affects golden retrievers and their cross breeds
-mutation of PNPLA1 gene that results in derangement of intercellular lipid barrier
-primary derm signs: mild to severe scales, small to large, white or brownish color, mostly ventral - ichthyosis type 2:
-novel additional mutation with ABHD5 gene stimulates esterification of omega-hydroxy ceramides with linoleic acid for AcylCer biosynthesis
-large white to grey and powdery to adherent scale throughout hair coat
-more severe than type 1 - treatment:
-applications of high concentrations of oral and/or topical fatty acids
-moisturizing shampoos: retain the moisture in the skin after bathing; humectic agents: urea, sodium laurate, etc.
-and antiseborrheic keratolytic shampoos to remove scales and strengthen skin barrier humidity
–kerato leti shampoos (new, hard to get, really dry out skin and remove scales)
describe AR congenital ichythosis in american bulldogs
- scruffy/discheveled hair coat compared with the smooth coat of normal littermates
- glabrous skin erythematous with tightly adherent light brown scales
- due to mutations in the NIPAL4 gene, which plays a role in lipid metabolism in the skin
- treatment resembles golden retreivers with ARCI
describe how antiseborrheic shampoos work
-keratoplastic shampoos: cytostatic effect on basal cells, reducing their rate of division (ex. sulfur)
-keratolytic shampoos: eliminate excess corneal layers by increasing desquamation due to ballooning of corneocytes that make stratum corneum softer and reduce the intercellular cohesion of corneocytes (ex. salicylic acid, benzoyl peroxide, glycerin)
describe classic sebaceous adenitis (a secondary cornification disorder)
- mechanism of lesion formation: destruction of sebaceous glands by cytotoxic T-lymphocytes
- signalment:
-standard poodles, akitas, havanese more predisposed but can affect anyone
-adult onset - lesions:
-cranio-caudal and dorso-ventral evolution: matting of hair, follicular casts (superficial follicular scales), partial hair loss
-clumps of adherent scales, adhering to hair shafts
-on head and pinnae, followed by trunk and tail, then spreads distally - dx:
-no ddx
-histopath biopsies of an area with follicular casts: accumulations of keratin and follicular material that adheres to the hair shaft extending above the surface of the follicular ostia
-hair plucks: easily epilated
-skin biopsy required for dx! - treatment:
-oral cyclosporine: T cel inhibitor (review side effects) for multiple months
-antiseborrheic and moisturizing shampoos
-prognosis: variable
describe equine sarcoidosis
- mechanism of lesion formation: still unknown but granulomatous inflammation encircled by lymphocytes targets skin and other organs
-but skin is most frequently affected in horses! - signalment:
-many breeds
-most >3 years old - clinical forms:
-localized: remains focused within the skin without systemic signs
-partially generalized: will progress to generalized
-generalized: may start with exfoliative dermatitis or with granulomatous inflammatory nodules in multiple organs - lesions:
-focal, multifocal, or generalized extensive scaling and crusting with varying degrees of alopecia - dx:
-ddx: when scaling is main symptom r/o dermatophilosis, dermatophytosis, and pemphigus foliaceus
-histopath of biopsies of affected areas: multifocal nodular to diffuse lymphogranuloatous dermatitis with MNGCs - treatment:
-topical and/or systemic glucocorticoids (prednisolone or dexamethasone); begin with immunosuppressive and then taper
-prognosis for partially gen or generalized is poor; good for survival with localized
describe type I zinc-responsive dermatosis
- mechanism of lesion formation: genetic defects in zinc absorption impair desquamation
-dietary interference with absorption: minerals, phytates - signalment:
-syndrome I: nordic breeds (siberian huskies and alaskan malamutes)
-syndrome II: young dogs
-syndrome III: old dogs? - lesions:
-adherent scales with or without inflammation on the pressure points of the legs, footpads, and around mucocutaneous junctions (eyes) - dx: histopath of biopsy of scaly area
- treatment:
-premium diet rich in fatty acids
-zinc supplementation
-low dose (physiologic dose) steroids may enhance clinical response with zinc supplementation
-prognosis generally good
describe exfoliative superficial pyoderma/superficial spreading pyoderma
- some cases of superficial pyoderma present with severe exfoliation, usually in the form of expanding epidermal collarettes
- exfoliation suspected to be due to staph exfoliatin toxins that cause stratum corneum separation
- pustules might not be seen in spite of massive exfoliation
-often a residual pigmentary macule or patch marks the site of previous lesions - treat like bacterial folliculitis or impetigo
describe malassezia dermatitis
- malassezia pachydermatitis:
-normal commensal of canine and feline skin (more abundant on skin of dogs with atopic dermatitis!)
-yeast commonly inhabit oral cavity, lip commissures, external ear canals, interdigital webs, perineum, anal sacs
-basset hounds and sphinx cats predisposed - in many cases:
-proliferate secondary to epidermal barrier defects that occur secondary to inflammation
-skin inflammation results in abnormal cornification, decreased epidermal defense system, and excessive sebum secretion, which contributes to overgrowth of commensal yeast +/- bacteria
-microbes the elicit secondary inflammation= autoaggravating loop - clinically:
-suspect malassezia when see erythema, scaling, greasiness, and malodor present ESPECIALLY in fold areas
-plus hyperpigmentation, crusting, lichenification - dx: surface cytology (smears, swabs, acetate-tape strips, etc.)
-clinical signs do NOT correlate to number of yeast seen (could be very few but very virulent little buggers) - treatment: symptomatic:
-address secondary underlying diseases: atopic dermatitis (#1), endocrine diseases, etc.
-ALWAYS topical therapy: degreasing shampoo, azole (miconazole)-containing shampoos and wipes, azole-chlorhexidine containing shampoos and wipes
-in RARE cases: systemic therapy for 2-3 weeks is added: ketoconazole, itraconazole, terbinafine
–side effects: GI upset and liver toxicity (azoles)
describe equine dermatophytosis
- due to trychophyton equinum, M. canis, T. mentagrophytes, and T. verrucosum
- topical treatment and environmental management as discussed for dermatophytosis
describe demodicosis due to long-bodied demodex/D. injae
- induced pruritis, erythema, greasy, scaly skin in small dogs
-esp Westie terriers and shi-tzus - lesions: usually dorsal or facial
-erythema, greasiness, scaling, pruritis
-dorsum may be more affected - this bug not associated with immunsuppression
- treat similar to alopecic demodicosis
describe exudative epidermitis
- greasy pig disease
-acute, often fatal blistering skin disease of piglets - commonly caused by S. hyicus
- resembles human staph scalded skin disease
describe cutaneous epitheliotrophic T-cell lymphoma
- great mimicker of other diseases like atopic dermatitis
- older dogs: can be itchy erythematous and scaling with hair exfoliation (exfoliative erythroderma)
-erosions, ulcerations, and crusting
-suspicious: sudden itchy that looks like allergies (allergies rarely come on suddenly at older ages) - skin biopsy is a diagnostic tool!
-neoplastic T cell infiltration of the epidermis, adnexal structures, and oral mucosa
