Dermatology - Alopecia Flashcards
Spontaneous Alopecia
4 types of spontaneous alopecia:
Spontaneous Alopecia
etiology of genetic defect alopecia
Genetic defect of hair shaft or hair follicle congenital hair loss
What are the dermatological and non-dermatological clinical signs of hypothyroidism?
Cutaneous Mucinosis: excessive production of mucin
Myxedema: non-pitting (when pressure applied) edema, tragic face
What 2 bacteria cause pyoderma in dogs?
Staphylococcus pseudointermedius & schleiferi
3 causes of hyperadrenocorticism
Pituitary tumor: keeps producing ACTH
AG tumor: keeps producing cortisol
What are the dermatological and non-dermatological clinical signs of hyperadrenocorticism?
systemic signs develop first!
- unique: Calcinosis cutis (firm plaque on skin), muscle weakness / atrophy
Alopecia patterns in hypothyroidism versus hyperadrencorticism
Hypothyroidism: Gradual alopecia @ areas exposed to a lot of friction: collared area, the tail, truncal area
Hyperadrenocorticism: Truncal alopecia, spares the head & extremities
Pathogenesis of alopecia in hypothyroidism versus hyperadrencorticism:
Hypothyroidism: due to reduction in thyroid hormones (and thus decreased metabolism), the hair follicle cycle is slowed down
Hyperadrenocorticism: due to excess endogenous glucocorticoids, hair follicles do NOT re-enter anagen phase -> hair follicle eventually undergoes atrophy and are spontaneously expelled
Alopecia X
- etiology
- signalment
- clinical signs
- lesions
- treatment?
- Unknown pathogenesis
- Genetic mutation? Hair follicles “stuck” in resting phase?
- pomeranians
- DDx with Cushing’s: Alopecia lesions develop earlier in age than Cushing’s, + no systemic signs!
- tx: cosmetic issue, not detrimental. microneedling?
Canine Flank Alopecia
- breeds predisposed?
- lesion location / characteristics
- Boxers, english bulldogs, airdale terriers, rhodesian ridgebacks
- lesions on the flank => hyperpigmentation
Color dilution alopecia
- pathogenesis
- diagnosis
- lesion location + what condition it mimics
- sequela
- genetic defect of melanin transfer (via melanocytes) to the hair follicles
- hair pluck + trichogram
- lesion starts in caudal-half of dog
- lesion similar to flea-allergy dermatitis
- 2º pyoderma; no specific tx
Telogen Effluvium
- pathogenesis
- lesion appearance
- sudden, metabolic stress (severe illness, surgery, postpartum, drugs), 3-4 weeks after the event
- generalized hair loss
Primary vs Secondary Alopecia
Differentials for folliculitis in spontaneous alopecia
- Demodicosis
- Dermatophytosis
- Bacterial Infection
What is the natural habitat and pathogenesis of demodicosis spp.?
Juvenile versus Adult Canine Demodicosis
Juvenile
- develops first 18 motnhs of life, localized and tx not required but may become generalized and require tx
- < 4 SKIN LESIONS (LOCALIZED)
Adult
- develops spontaneously OR due to spotaneous alopecia coniditons (immunosuppression conditions – hypothyroidism, cushing’s, chronic steroid use)
- ≥ 5 SKIN LESIONS (GENERALIZED), +/- deep pyoderma!
Not typically pruritic, unless it develops into 2º pyoderma or hose rxn to mites
Compare and contrast Demodex canis and Demodex injai
Similarities:
- both mites cause canine demodicosis
- both produce similar skin lesions
Differences:
- D. injai mites are long-bodied and over 2x the length of D. canis
- D. injai mites are found mainly in sebaceous ducts & glands
- D. injai mites produce greasiness on the dorsal trunk
How to diagnose Canine Demodicosis
- Deep skin scrapings from multiple sites
- Trichogram
- Exudate smear impression
- Adult onset: investigate if there is an underlying cause
Adult ≤ 30% of cases, the underlying condition cannot be determined!
Canine Demodicosis treatment and how long treatment trial
Bravecto, Simparica, Nexgard; continue until 2 skin scrapes / hair plucks, ONE MONTH APART, do NOT yield mites and eggs. Clinical “cure” only considered after ONE YEAR w/out recurrence
What are the 2 types of demodex sp. in CATS?
- Demodex cati - FOLLICULAR MITE - adult onset, with underlying disease/immunosuppressed condition! (FIV/FeLV, steroids)
- Demodex gatoi - STRATUM CORNEUM MITE- causes intensepruritis & is *contagious!!
Demodex cati lesions versus demodex gatoi
Demodex cati: non-pruritic alopecia lesions, can visualize mites on deep skin scrape or hair pluck
Demodex gatoi: intensely pruritic lesions, generalized puritis, difficuly to visualize the mites!
Dermatophytois - ZOONOTIC!!
Most common fungus in cats versus dogs
M. canis (cats)
Trichophyton mentagrophytes (dogs)
M. gypseum (geophilic - in soil)
How is dermatophytosis transmitted?
- Direct contact; fomites!;
- Cats = asymptomatic carriers / reservoirs!
Characterisitics of dermatophytosis lesions
Focal/localized that expand centrifugally
Lesion can become generalized if not diagnosed early enough, or if mis-diagnosed for a condition treated with glucocorticoids
How is Dermatophytosis diagnosed (4 methods)?
- Wood’s Lamp (M. canis fluoresce)
- Trichogram (fungal spores, hyphae visualization)
- Fungal culture (Dermatophyte Test Medium: color change from yellow -> red – fungus metabolizes the protein in the media) + microscopic examination of colony
- PCR (DNA presence = true infection versus fomite contamination versus non-viable spores deteced)
Dermatophytosis treatment
Patient: Topical treatment + Systemic treatment (Ketoconazole, fluconazole, itraconazole, etc.)
Environment: prevent spread of infection (zoonotic!), prevent false positive DTM and PCR via washing bedding, brushes, rugs, etc. 1:10 to 1:100 dilute chlorine bleach
How does ischemia cause spontaneous alopecia?
The blood vessels provide nutrients required for vitality to the skin / hair follicles -> SF ischemia causes alopecia, deeper ischemia causes erosion-ulceration, and muscle-level affected ischemia causes myositis
Which vaccine has been associated with vaccine-associated alopecia?
Rabies vaccine
Which breeds are predisposed to dermatomyositis? How is it diagnosed and treated?
Collies & shetland sheepdogs
Diagnosis = skin biopsy
Tx = immuno-suppressive doses of cyclosporin
Skin lesion appearance in Generalized ischemic dermatopathy? Diagnosis & tx?
Nearly identical to dermatomyositis, except lesions are generalized (vs. solely face/muzzle)
Diagnosis = skin biopsy
Tx = immuno-suppressive doses of cyclosporin
