Unit 1: Alopecic Disorders of Dogs & Cats Flashcards
What is the cuticle?
Outermost layer that has a fish scale appearance, is up to 10 layers thick
What is the cortex?
Middle layer where the pigment is contained;
Clear appearance, contributes to sheen
What is the medulla?
Innermost layer of vacuated cells;
Degeneration of glycogen that builds up and contributes to sheen;
Contributes to insulating capability
What is the bulb?
Active part of the follicle that causes growing
What is the isthmus?
Middle portion of the follicle that is affected by some AI diseases
What is the bulge of the follicle?
Area where the sebaceous glands empty into
What is the infundibulum of the follicle?
Opening surface down to where the sebaceous glands open
What is the hair cycle?
Anagen –> Catagen –> Telogen –> Exogen
_____ is the active growing phase.
anagen
_____ is the transition from growing to non-growing hairs.
catagen
____ is the resting phase.
telogen
Majority of hairs in dogs and cats are in _____ phase.
telogen
_____ is active shedding of the follicle.
exogen
What growth phase is this?
telogen
What growth phase is this?
anagen
What should the ratio of telogen : anagen be?
10-20 : 1
What hormones stimulate hair growth?
Thyroid, melatonin, growth hormone, androgens
What hormones inhibit hair growth?
Cortisol, estrogen, progesterone, prolactin
What breed is this and why are they hairless?
Chinese Crested - autosomal dominant trait
What breed is this and why are they hairless?
Mexican hairless - autosomal dominant trait
What happens if the Mexican Hairless has homozygous dominant alleles?
It is lethal
What breed is this and what is special about them?
Peruvian Inca Orchid - oldest dog breed on record
What breed is this and why are they bred for?
American Hairless Terrier;
Bred for “hyperallergenicity” but allergens are actually in the saliva not the hair
What breed is this and what are the characteristics?
Devon Rex;
Primary hairs resemble secondary hairs
Whiskers absent or stubbled
Bald ventral surfaces
What breed is this and what are the characteristics?
Cornish Rex;
Lack primary hairs, whiskers are short and curly
What breed is this and what are the characteristics?
Sphinx;
Have hair follicles and hair fiber
hair doesn’t form normally, fracture before they get to the surface
What alopcic conditions are not treatable?
X-linked/Congenital, canine pattern alopecia, Black Hair Follicular Dysplasia, Color Dilution Alopecia, Breed-Specific Acquired Alopecia
What is X-linked/Congenital alopecia?
Genetic mutation with ectodermal differentiation, recessive x-linked gene (males affected)
What are characteristics of congenital alopecia?
Varying degrees affecting the head, scral resion, abdomen, and proximal extremities
What are characteristics of canine pattern alopecia?
Onset of 6 months, ventral type vs. pinnal type (3-5 yo) vs. alopecia/melanoderma of the Yorkie
What is the treatment for canine pattern alopecia?
None; it is a cosmetic problem
What are characteristics of black hair follicular dysplasia/color dilution alopecia?
Affects black hair or dilute colors - Dobermans, Silver Labs
How is black hair dysplasia/color dilution alopecia diagnosed?
Trichogram - clumping of melanin –> weakening and fracturing of hair
What breeds get Breed Specific Acquired Alopecia?
Chesapeake bay Retrievers, Curly-Coated Retrievers, Portuguese Water Dog, Irish Water Spaniel
What areas are affected by breed specific alopecia?
Flanks, dorsum, rump, caudal thighs
What is characteristic of alopecia in the Irish Water Spaniel?
Bald neck and tail
What alopecic conditions MIGHT be treatable?
Canine Recurrent Flank Alopecia, Bald Thigh Syndrome, Alopecia X
What is Canine Recurrent Flank Alopecia AKA?
Seasonal Flank Alopecia
What breeds commonly get seasonal flank alopecia?
Boxer, English Bulldog, Airedale Terrier, Schnauzer
What are characteristics of seasonal flank alopecia?
Onset at 4 yo, rapid onset of well-demarcated flank alopecia and hyperpigmentation
How is seasonal flank alopecia diagnosed?
History, CS, exclusion, biopsy
How can seasonal flank alopecia be treated?
Spontaneous regrowth or melatonin to try to prevent episodes from recurring the following year
What breed gets bald thigh syndrome?
Greyhounds 2-3 yo
What is the potential treatment for bald thigh syndrome?
Regrowth of hair observed in some cases after racing career has finished
What breeds are affected by Alopecia X?
Pomeranians, Malamutes, Chows, Keeshonds 1-3 yo
What are the CS of Alopecia X?
Symmetrical, hyperpigmentation sparing the head and limbs
What is the diagnosis for Alopecia X?
exclusion
What is the treatment for Alopecia X?
Benign neglect, neutering, melatonin, pumice stone?
What are characteristics of hypothyroidism?
Dull/dry/brittle hair, symmetric alopecia, bridge of nose and tail affected, pyoderma and otitis possible, facial myxedema
What is the cause of hypoT4?
primary most common
What tests can be used to diagnose hypoT4?
tT4, fT4, TSH, TgAA
What CBC findings are consistent with hypoT4?
Normocytic, normochromic, non-regen anemia
What chem findings are consistent with hypoT4?
hypercholesterolemia, hypertriglyceridemia, elevated ALT/CK
What diagnostic is normal in hypoT4?
U/A
What characteristics are associated with Cushing’s?
Generalized alopecia, thin skin, comedones, calcinosis cutis, pyoderma
What is Cushing’s caused by?
Pituitary or adrenal tumor
What tests are used to diagnose Cushing’s?
LDDS (slower), ACTH stim (faster, $$)
What CBC findings are consistent with Cushing’s?
Leukocytosis, neutrophilia, lymphopenia, eosinopenia, thrombocytosis
What chem findings are consistent with Cushing’s?
Elevated ALP +/- ALT
What U/A findings are consistent with Cushing’s?
Low USG, bacteriuria, elecated UCCR ratio
What is the treatment for Cushing’s?
Trilostane or Mitotane
What are characteristics of hyperestrogenism?
Alopecia of abdomen, thighs, perineal region
Linear preputial dermatosis = pathognomonic
Feminization is more common with _____.
cryptorchids
What causes hyperestrogenism?
Ovarian cysts/tumors, diethylstilbestrol administration, Sertoli cell tumors, accidental hormone exposure
How is hyperestrogenism diagnosed?
Signalment, history, CS, serum estradiol
What CBC findings are consistent with hyperestrogenism?
Non-regen anemia, leukopenia, thrombocytopenia
What diagnostic tests are normal with hyperestrogenism?
Chem and UA
_____ effluvium is acute onset of hair loss due to antimitotic drugs.
anagen
_____ effluvium is not as rare, due to stressful event, and hair loss is noted _____ after insult.
Telogen; 1-3 months
What is post-clipping alopecia?
Lack of hair regrowth after close clipping for catheters and surgical sites; NOT disease
What breeds are predisposed to post-clipping alopecia?
Huskies, Malmutes, Samoyeds, Chows
Why does post-clipping alopecia happen?
Breeds have prolonged telogen phases, so only “treatment” is to give the hair time to grow back
