Non-inflammatory Alopecic diseases Flashcards
Causes of alopecia
- Traumatic (Allergies, parasites, pruritic pyoderma, Malassezia)
What re causes of hair falling out from folliculitis?
- Pyoderma
- Demodex
- Dermatophytosis
- Also sebaceous adeniti
Non-inflammatory causes of alopecia from hair cycle arrest
- Endocrine
- Alopecia X
- Cyclic flank alopecia
- Pattern alopecia
Non-inflammatory causes of alopecia from dystrophies/dysplasias?
- Congenital hypotrichosis
- Color dilution alopecia
- Black hair follicular dysplasia
Benefits of hair
- Thermal insulation/regulation
- SEnsory perception
- Barrier protection
- Camouflage
- Social communication
What is primary hair?
- Undercoat or guard
What are secondary hairs?
- Undercoat
Do cats have more primary or secondary hairs?
- More secondary hairs, which is why they are softer
Do puppies lose their undercoats?
- No, they gain adult coats
What are the three phases of the hair cycle?
- Anagen
- Catagen
- Telogen phase
Anagen phase - what’s happening?
- Active growth
- Producing new cells and keratin
Catagen phase - what’s happening?
- Stops growing
- Detaches slowly
Telogen phase - what’s happening?
- Resting phase
- Prepares the next cycle
What controls the hair cycle (and what is most important?)
- Photoperiod (very important)**
- Ambient temperature
- Nutrition
- Genetics
- Hormones
When is activity and hair growth maximal or minimal?
- Maximal in summer
- Minimal in winter
What causes increased shedding?
- Increased with artifical light
- Telogen hairs
- Disease states
What type of cycles do most humans poodles have?
- Anagen cycles
WHat type of hair cycles do most dogs have?
- Telogen cycles
Is telogen a pathologic state?
- No
Are telogen hairs easy to pull out?
- Not necessarily
What hormone accelerates anagen hairs?
- Thyroid hormones or growth hormone
What hormones inhibit anagen?
- Glucocorticoids/estrogens
- Suppress hair growth rate
How long does hair take to regrow on a short coated dog?
- 3-4 months
How long does hair take to fully regrow on a long-coated dog?
- UP to 18 months
What are alopecic breeds?
- Chinese crested
- Xoloitzcuintle
- Sphinx cat
Congenital hypotrichosis - what causes?
- Not well understood
Congenital hypotrichosis - by what point do they lose their hair?
- Either brn with no hair or lose hair within the first month
-
Breeds with congenital hypotrichosis
- Chihuahua, poodles, GSD
How to differentiate congenital hypotrichosis
- Look for signs of active inflammation
Color dilution alopecia - what causes
- ALopecia associated with coat color dilution gene
What color hair coats associated with color dilution alopecia?
- Blue or fawn colored hair coats
Breeds associated with color dilution alopecia
- Dobermans
- Great Danes
- Dachshunds
- Italian Greyhounds
When do clinical signs start with color dilution alopecia?
- 6 months to three years
Clinical signs associated with color dilution alopecia, and where do they show up?
- Alopecia
- Seborrhea
- Pyoderma (papules, pustlues, crusts, epidermal collarettes)
- With the trunk most severe
What underlying causes of pyoderma should you look for even with color dilution allopecia?
- Allergy or endocrine
Diagnosis of color dilution alopecia
- Microscopic examination of the hair r(trichogram) reveals melanin clumping resulting in distortion of the hair shaft
- Histopath reveals abnormal melanin clumping within the hair shaft and periadnexally
Treatment for color dilution alopecia
- Symptomatic therapy for seborrhea and antibiotics for pyoderma
- Melatonin may possibly help stimulate hair growth but mechanism unknown
How common is black hair follicular dysplasia?
- Uncommon
Age of dog with black hair follicular dysplasia?
- Young dogs
- Often born normal but show changes within 4 weeks
WHere are the lesions with black hair follicular dysplasia?
- Only black hairs affected
Histopathology for black hair follicular dysplasia?
- Same as with color dilution alopecia
- Abnormal melanin clumping within the hair shaft and periadnexally
Trichogram for black hair follicular dysplasia?
- Not helpful because the hairs are too dark (black)
What is the major problem with most hair cycle abnormalities?
- Hairs remain in telogen and fail to enter anagen
Factors that influence hair cycle
- genetics
- Trauma
- Intrinsic factors (growth factors)
- Extrinsic factors (endocrine, immunologic, metabolic)
Diseases associated with hair cycle abnormalities
- Endocrine dermatoses (hypothyroidism, Cushing’s)
- Alopecia X
- Cyclic flank alopecia
- Pattern alopecia/baldness
- Anagen/telogen defluxion
- Post clipping alopecia
Clinical signs associated with hair cycle abnormalities ? Are any of these specific for hair cycle abnormalities?
- ALopecia (bilateral and symmetrical)
- Dull, dry, brittle hairs
- Failure to regrow hair
- Increased pigmentation
- Seborrhea
- Comedomes
- SEcondary infections (yeast, pyoderma)
- Nonpruritic usually unless pyoderma, seborrhea, or yeast dermatitis present
Histological characteristics
- Hyperkeratotis (epidermal, follicular)
- Epidermal hyperkeratosis clinically seen as seborrhea
- Follicular hyperkeratotis clinically seen as comedoems
- Follicular dilation (filld with keratin)
- Follicular atrophy
- Telogen hairs
- Epidermal melanosis
- Epidermal atrophy (more common for Cushing’s)
Are biopsy findings with hair cycle disorders specific?
- No, they cannot differentiate endocrine diseases from other causes of non-inflammatory alopecias
HPA axis
- Hypothalmus releases thyrotropin releasing hormone
- TRH on pituitary causes release of Thyroid stimulating hormoen (TSH)
- TSH on thyroid gland causes release of T4, T3, and RT3
- Negative feedback possible with TSH on hypothalamus and the thyroid hormones on both the pituitary and hypothalamus
Where do primary, secondary, and tertiary hypothyroidism affect the animal?
Which is most common?
- Primary (most common - thyroid gland)
- SEcondary (pituitary gland)
- Tertiary (hypothalamus)
What is primary hypothyroidism?
- Lack of functional thyroid tissue
- Most common form >95%
What is most common cause of primary hypothyroidism?
- Acquired
- Lymphocytic thyroiditis ~50%
- Idiopathic follicular atrophy
- Least likely to be secondary neoplasia
Iatrogenic causes of primary hypothyroidism
- Surgery
- Radioactive iodine therapy
- Anti-thyroid medications
How common is congenital primary hypothyroidism?
- Rare
Cretinism
- Thyroid gland agenesis or dysgensis
- Dyshormonogenesis (thyroid peroxidase deficiency)
- Deficient dietary iodine
- Ingestion of goitrogens
Why don’t you see congenital primary hypothyroid ism that often?
- Early death so may go undiagnosed
- Disporportionate dwarfism
Secondary hypothyroidism
- Imparied secretion of TSH from the pituitary gland
Acquired causes of 2° hypothyroidism
- Neoplasia
- Illness, malnutrition
- Pituitary suppression, e.g. glucocorticoid administration
Congenital causes of 2° hypothyroidism
- Cystic Rathke’s pouch
- Other pituitary hormone deficiencies, e.g. ADH
Tertiary hypothyroidism
- Lack of TRH in the hypothalamic supraoptic and paraventricular nuclei
- Never documented in the dog
Signalment of hypothyroidism
- RARE under one year
- Peak incidence around 4-6 years
- No sex predisposition
- Dobies, Golden and Labrador Retrievers, Dachshunds, Cocker Spaniels
Clinical signs of hypothyroidism
- Vague, diffuse, gradual onset
- Not pathognomonic for the disease
- Most common is dermatologic and metabolic
- General appearance: dullness, lethargy, exercise intolerance, obesity without history of polyphagia, cold intolerance (“heat seekers”_
Dermatologic signs with hypothyroidism
- > 85% of dogs
- Dry skin and hair coat (seborrhea)
- Alopecia in areas of wear/pressure points
- Rat tail or bridge of nose
- Bilateral symmetrical alopecia
- Dull, dry, brittle hair (retained in telogen phase)
- Lose primary hairs and retain guard hairs
- Failure to regrow hair after clipping
- Hyperpigmentation in alopecic areas
- Seborrhea, lichenification, comedones
- Generally non-pruritic
- Myxedema
- REcurrent infections
Why do dogs with hypothyroid have wear of their hair?
- Thyroid hormones needed for initiation of anagen phase
What is myxedema?
- Severe cases
- Excess mucopolysaccharides (+hyaluronic acid in dermis)
- Results in tragic facial expression (more advanced often)
Recurrent infections with hypothyroidism
- Otitis externa
- Pyoderma
- Effect on immune system
- Effect on barrier function
- may be their only sign
Other clinical signs with hypothyroidism
- Cardiovascular effects
- Ocular abnormalities (rare)
- Neurologic abnormalities (from segmental demyelinization)
- GI abnormalities
- REproductive abnormalities
- Myxedema coma
Diagnostic tests for hypothyroidism
- No single test (rarely confirm with biopsy)
- Evaluate all data (signalment, history, clinical signs, physical exam, clinicopathologic data, thyroid ohrmone concentrations; reponse to thyroid supplementation)
- Hypothyroidism tends to be overdiagnosed
- T4, free T4, TSH measurements
Which drugs alter thyroid hormones?
- Glucocorticoids
- TMS antibiotics
How do glucocorticoids affect thyroid hormones?
- Decrease TT4, free T4
- Decrease T4 to T3 conversion
- Decrease TSH
- Could cause a false positive I think
How do trimethoprim-sulfa antibiotics alter thyroid hormones?
- Inhibits iodine conversion
- Decrease TT4, decrease free T4, and increase TSH
- True but reversible hypothyroidism
Diagnosis of hypothyroidism
- Compatible clinical signs
- Low to low normal TT4
- Low free T4
- Elevated TSH with low T4, low free T4
- Response to therapeutic trial
Medication for treatment of hypothyroidism
- L-thyroxine
HPA axis for cortisol
- Hypothalamus stimulates corticotropin releasing hormoen onto pituitary gland
- Pituitary gland releases ACTH onto the adrenal glands
- Adrenal glands release cortisol, which has a negative effect on the pituitary and CRH
Appearance of adrenal glands with pituitary dependent hyperadrenocorticism
- With pituitary dependent it produces a lot of ACTH and causes hypertrophy of the adrenal glands
Appearance of adrenal glands with adrenal dependent hyperadrenocorticisim
- One is overproducing cortisol, which then goes back and has negative feedback on the hypothalamus and pituitary gland
- This results in atrophy of the unaffected adrenal gland
What are the five P’s of hyperadrenocorticism?
- Polyuria
- Polydipsia (interference with release and action of ADH)
- Polyphagia (direct effect of glucocorticoids)
- Pot belly (intraabdominal fat, hepatomegaly, full urinary bladder, lax abdominal muscles)
- Panting or tachypnea
Causes of panting with Cushing’s
- THoracic fat
- Abdominal distention
- Muscular weakness
- Thromboembolic complicatiosn
- Many small breed dogs also have mitral insufficiency, collapsing trachea, etc.
Appearance of alopecia with Cushing’s
- Bilateral, symmetric
- Often spares head and extremities
- Atrophy of hair follicles
- Nonpruritic
- May fail to regrow their hair
- Hyperpigmentation
Common age of dogs with Cushing’s
- Middle to older dogs
Common breeds for hyperadrenocorticism
- Bostons, Dachshunds, Boxers, Shih tzus
Dermatologic signs with Cushing’s
- Bilateral symmetrical alopecia sparing head and distal extremities
- Dermal atrophy (thin epidermis and dermis)
- Recurring pyodermas**
- Demodicosis
- Milia
- Calcinosis cutis
- Poor wound healing
- Bruising or petechia from minmimal trauma due to blood vessel fragility
What may be the only sign associated with Cushing’s?
- Recurrent pyodermas
What are the 5 P’s?
- Polydipsia
- Polyuria
- Polyphagia
- Panting
- Pendulous abdomen
Other clinical signs associated with Cushing’s
- Urinary tract infections
- Muscle atrophy
- Generalized weakness
More serious complications with Cushing’s
- PTE
- Cerebral infarct
- Glomerulonephritis
- Hypertension
- Opportunistic infections
- Diabetes mellitus
- Acute pancreatitis
- Pyelonephritis
- Pituitary macroadenomas
What should you immediately think with dermal atrophy or milia?
- You really should be thinking steroids
Comedomes
- Keratin plugged follicles
Signs associated with pyoderma
- Papules
- Pustules
- Crusts
- Epidermal collarettes
- patchy alopecia
- +/- Pruritus
Diagnosis of Cushing’s
- History
- Clinical signs
- Minimum data base (CBC/Chem/UA
CBC signs with Cushing’s
- Lymphopenia and eosinopenia
- Monocytosis and neutrophilia
Chemistry changes with Cushing’s
- ALP elevated (85-95%)
- Mildly elevated ALT
- Cholesterol
UA changes with Cushing’s
- Dilute
Screening tests for Cushing’s
- ACTH Stimulation test
- Low dose dexamethasone suppression test
- Urine cortisol to creatinine
Differentiating tests
- Sometimes LDDST
- HDDST
- Endogenous ACTH
- Advanced imaging (AUS/CT/MRI)
Treatment of HAC
- Trilostane (not benign; need to make sure diagnosis is correct)
- Lysodren
Who gets Alopecia X?
- Pomeranians
- Poodles
- Nordic breeds
Age of dogs with alopecia X?
- 1-10 years of age
Sex of dogs with Alopecia X?
- Males and females equally
Clinical signs of Alopecia X?
- Symmetrical alopecia sparing head and extremities**
- Loss of guard hairs progressing to complete alopecia of the neck, tail, rump, perineum, caudal thighs, and ultimately trunk
- No systemic illness
- Diffuse hyperpigmentation (owners breeders falsely refer to it as Black Skin Disease)
Pathomechanism of Alopecia X?
- Unknown
- Defect of anagen hair cycle?
Diagnosis of Alopecia X?
- Rule out other causes of endocrine alopecias
- Hypothyroidism and Cushing’s
- +/- biopsy to rule out sebaceous adenitis
Treatment possibilities for Alopecia X?
- Melatonin (most benign treatment; up to 40% may regrow hair); may take 3-4 months
- Neutering of intact dogs (castration responsive dermatosis)
Treatments NOT recommended for Alopecia X?
- Trilostane (not without potential for side effects)
- Lysodren (high potential for side effects)
- Growth hormone (can cause diabetes)
- Progesterone
- Testosterone (high potential for side effects)
WHen does pattern alopecia typically start?
<1 year of age
Progression of pattern alopecia/
- Typically born with normal hair coat then develops alopecia
What are the four syndromes of pattern alopecia?
- Pinnal alopecia of dachshunds
- Ventral and caudal alopecia of Dachshunds and Boston Terriers (no inflammation, excoriations, pustules, papules, crusts)
- Pattern alopecia of Portugese water dogs and American water spaniels (could be an allergy, so look at the skin)
- Bald thigh syndrome of greyhounds
When does cyclic flank alopecia tend to occur?
- Develops during periods of short day length (fall/winter/spring)
What can resolve cyclic flank alopecia? Is it always effectie?
- UV light exposure
- Not always
Breed predispositions for cyclic flank alopecia
- Airedales
- Boxers
- English Bulldogs
- Can be hyperpigmented
- Serpiginous (all over)
Diagnosis of cyclic flank alopecia
- Consider/rule out endocrine causes
- Hypothyroidism
- Cushing’s disease
- Skin biopsy shows follicular keratosis; deformed follicles that are unusual telogen follicles described by pathologists
Where is cyclic flank alopecia most often seen/
- PNW and northern parts of the US
Age of dogs with seasonal trunk alopecia or cyclic flank alopecia?
- 1.5-4.5 years
What is “witches foot”?
- Deformed telogen follicles described by pathologists
Treatment for cyclic trunk alopecia
- Melatonin may shorten duration and prevent recurrence
- Increase UV sunlight
- Benign neglect
Biopsy of pattern alopecia/baldness
- Small miniature sized follicles and adnexa
- Small anagen hairs
- Not always definitive
Treatment for pattern alopecia/baldness
- Melatonin?
- Benign neglect
Excessive shedding - when is normal shed cycle?
- spring and fall
In normal shedding, what should not be created with epilation?
- Alopecic area
What can cause more shedding?
- Hyperexcitable or nervous animals
What should you check for if there has been a change in shedding?
- Endocrinopathies
What to do for excessive shedding
- Remove the dead hairs, diet changes, increased free fatty aids, adjust light and/or temperature
