Alopecia Flashcards
Compare primary and secondary alopecia
- Primary: failure to grow normally
- Secondary: grows normally but subsequently damaged or lost
What are the mechanisms of primary alopecia?
- Lack of stimulation of growth
- Abnormal growth factors
- Elongation of telogen phase
Define true alopecia
Direct damage to the hair follicle unit, leading to loss of the whole hair follicle unit
Define apparent alopecia
Hair shaft damaged but not lostr from hair follicle unit
How should a case of apparent alopecia be investigated?
No damage to hair follicle unit, check this on trichogram. Likely due to pruritus so investigate as pruritus case
Identify the potential causes for true alopecia
- Hair follicle inflammation e.g. folliculitis, furunculosis, bulbitis. Hair follicle unit damaged
- Hair cycle abnormality e.g. endocrine
- Hair morphological abnormalities: hair malformed, breaks off
- Congenital aplasia: never grows
List the lesions commonly associated with alopecia
- Pustules
- Comedones
- Follicular casts
What would pustules associated with alopecia be suggestive of?
- Pyoderma
- Autoimmune disease
What would comedones associated with alopecia be suggestive of?
- Demodicosis
- Dermatophytosis
- Hypothyroidism
- HAC
- Long term glucocorticoid use (iatrogenic Cushings)
What would follicular casts associated with alopecia be suggestive of?
- Follicular disease
- bacterial infection (pyoderma)
- Demodicosis
- Sebaceous adenitis
- Primary keratinisation disorder
- Endocrinopathy
Describe sebaceous adenitis
- Immune mediated attack on sebaceous glands
- Occurs in certain breeds esp. poodles and poodle crosses
What is primary keratinisation disorder?
Body genetically programmed to produce lots of keratin inappropriately
Describe the appearance of follicular casts
- When hair is epilated, comes out in clumps surrounded by keratin
- Can be subtle (1 or 2 hairs) or whole collars
What conditions would you be most suspicous of in an animal with alopecia that started <1yo?
- Demodicosis
- Dermatophytosis
- Superficial pyoderma
- Congenital alopecia
What conditions would you be most suspicious of in an animal with onset of alopecia when middle aged/older?
- Endocrinopathies
- Neoplasia
Give some examples of breed specific hair loss
- Small terriers/boxers: predisposed to HAC
- Dachshunds: pattern baldness
- Doberman: dysplastic hair follicle diseases
Give an example of a cause of alopecia in entire males
Sertoli cell cell tumours
Give an example of a cause of alopecia in entire females
Post-partum telogen defluxion (hair loss after whelping, common for bitches, will grow back)
Give examples of how general history can indicate specific causes of alopecia
- PUPD: HAC
- Weight gain, lethargy: hypoT
- Small hunting dogs: trichophyton infection
- Lesions on owner/in contacts: dermatophytosis, ectoparasites
What aspects of the dermatological history can indicate specific causes of alopecia?
- Hair growth after clipping
- Seasonality
- Response to past treatment
- Pruritus
What conditions would lack of hair regrowth after clipping be suggestive of?
- HypoT
- Post clipping alopecia (unknown cause, common in plush coated dogs, can take extremely long to grow back or never)
What condition would you be suspicious of in a dog with bilaterally symmetrical alopecia, obesity, bradycardia, lethargy and lack of regrowth following clipping?
Hypothyroidism
How do Sertoli cell tumours cause alopecia?
Produce excessive oestrogen causing endocrinopathies
List the differentials for localised alopecia
- Key: Demodicosis, dermatophytosis, superficial pyoderma
- Post-clipping alopecia
- steroid injection/post-vaccine vasculopathy, rabies vaccine
- Tail gland hyperplasia on older male dogs
- Cicatricial alopecia (scarring)
- traction alopecia (top knot too tight on Westies)
List the differentials for multi-focal/diffuse patchy alopecia
- Key: demodicosis, dermatophytosis, superficial pyoderma
- Others: dermatomyositis, sebaceous adenitis, alopecia areata
What is alopecia areata?
An autoimmune condition that causes bulbitis
Explain what is meant by coat colour linked follicular dysplasia
- Colour dilution alopecia
- Paler than normal
- Hairs often weaker and break off leading to alopecia
In all cases of alopecia, what are the top 3 differentials?
- Demodicosis
- Dermatophytosis
- Superficial pyoderma
List the potential infectious causes of alopecia
- Pyoderma
- Dermatophytosis
- Demodicosis
- Leishmaniasis
List the iatrogenic causes of alopecia
- Anagen defluxion
- Post-clipping alopecia
List the endocrinopathic causes of alopecia
- Hypothyroidism
- HAC
- Recurrent flank alopecia
- Hyperoestrogenism in males (Sertoli cell tumour)
- Hyperoestrogenism in females (ovarian cysts)
- Alopecia X
- Other sex-hormone related
List causes of alopecia other than infection, iatrogenic, endocrinopathic or coat-colour linked
- Follicular dysplasia
- Telogen defluxion
- Pattern alopecia
- Sebaceous adenitis
- Epitheliotropic lymphoma
What tests are typically used in the investigation of alopecia?
- Trichogram
- Skin scrapings (all cases)
- Dermatophyte culture
- Wood’s lamp
When is dermatophyte culture typically used in the investigation of alopecia?
- All cases of focal/multifocal alopecia
- Young/elderly/immunosuppressed
- Small hunting dogs, esp. on face
- Dogs in household with cats
- In contact people with lesions
- High risk of zoonotic infection (living with children, elderly, immunocompromised)
- If follicular casts are seen
If no definitive diagnosis is made from the initial investigations of alopecia, what are the next steps?
- Rule out pyoderma
- Cytology of impression smears, pustule contents
- Assess response to 3 week course of appropriate antibiotic or anti-bacterial baths
If no response to antibacterial treatment for alopecia and pyoderma is ruled out, what are the next steps in the diagnosis of the cause alopecia?
- Endocrine function tests if endocrinological cause suspected
- Skin biopsy
Describe the use of skin biopsy in the investigation of alopecia
- Sample variety of sites, early lesions if possible, middle and periphery of expanding lesions, adjacent apparently normal area
- Wedge biopsy across margin
- Mark direction of hair growth
Describe the histological appearance of endocrinopathic causes of alopecia on biopsy
- Atrophic pattern
- Atrophy of epidermis, hair follicles and sebaceous glands
- Orthokeratotic hyperkeratosis and follicular keratosis evident
What signs are commonly seen prior to alopecia, where the underlying cause is an endocrinopathy?
- Ceruminous otitis
- Recurrent microbial infection
- Generalised seborrhea
- Proceed to hairloss usually in 6 months
List the common signs of hypothyroidism
- Dull, dry hair coat
- Hypotrichosis
- Seborrhoea
- Lack hair growth post-clipping
- Weight gain
- Lethargy/mental dullness
List the uncommon signs of hypothyroidism
- Alopecia
- Pyoderma
- Ceruminous otitis externa
- Facial myxoedema
- Wekaness
- Exercise intolerance
- Cold inteolerance
- Ocular disorders
- Bradycardia
List the rare signs of hypothyroidism
- Hypothermia
- Reproductive disorders
- Facial nerve paralysis
- Laryngeal nerve paralysis
Compare the alopecia seen in hypothyroidism and hyperadrenocorticism
HAC generally more symmetrical alopecia than hypoT. HypoT often shiny nose
Describe the dermatological changes commonly seen with HAC
- Symmetrical alopecia, sparing extremities
- Poor hair re-growth
- Comedones, seborrhoea
- Skin thinning, reduced elasticity
- secondary microbial infection/demodicosis
- Macular hyperpigmentation on ventrum
Describe the uncommon dermatological signs seen with HAC
- Coat colour changes
- Hyperpigmentation
- Calcinosis cutis
- Excessive bruising and poor wound healing
In what dogs does alopecia X most commonly occur?
- Young, 2-5yo
- Chows, Pomeranians, Samoyed, Husky, MIniature poodle
Describe the appearance of alopecia X
- Alopecia startin at the trunk/perineum, then spreads all over
- Head and limbs spared
- Remaining “puppy-like” coat
How is alopecia X diagnosed?
Diagnosis by elimination of other endocrinopathies and biopsy
Outline the treatment for alopecia X
Suggested:
- Castration
- Oral melatonin
- Deslorelin implants
Describe the clinical signs of Sertoli cell tumours
- Alopecia, hyperpigmentation
- Gynaecomastia (enlargement of mammary glands)
- Linear preputial erythema (red line along prepuce)
- Attraction to other male dogs
- Occasional bone marrow suppression
What treatment is indicated for Sertoli cell tumours?
Neutering (check for metastasis first)
What is canine recurrent flank alopecia?
A common condition of alopecia associated with photoperiod, usually onset Nov-March
Describe the signalment for canine recurrent flank alopecia
- Mean onset 4yr, range 1.5-11yr
- Breeds predisposed: Boxers, Airedale, English bulldog, Schnauzer, Rhodesian ridgeback
Describe the appearance of canine recurrent flank alopecia
- Usually thoracolumbar
- Abrupt onset
- Well demarcated alopcia
How is canine recurrent flank alopecia diagnosed?
- Rule out hypoT, HAC, other follicular dysplasia
- Use endocrine tests and biopsy
Outline the treatment of canine recurrent flank alopecia
- Usually benign to no treatment, normally regrows spontaneously in 3-8mo
- Oral melatonin (unlicensed) may be used at onset of alopecia
- Warn owner of recurrence, but may not be yearly
What is anagen defluxion?
Abrupt cessation of mitosis in anagen
What is anagen defluxion usually associated with?
- Severe systemic disease
- Cytotoxic drugs e.g. chemotherapy
- Toxins (e.g. selenium, rare)
What is telogen defluxion?
Hair follicles go into premature telogen
What is telogen defluxion usually associated with and how is it diagnosed?
- stressful events e.g. pregnancy, parturition, lactation, anaesthesia
- Regrow in several months once stressor removed
- Diagnosed on biopsy
Which breeds are predisposed to pattern baldness in the following locations:
a: pinnal
b: caudal thighs
c: post-auricular, ventral neck, ventrum, caudomedial thighs
a: Dachshunds
b: Greyhounds
c: Dachshunds, greyhounds, chihuahua
How is pattern baldness diagnosed? Treatment?
- Biopsy, suspect based on breed, clinical appearance and lack of anything else
- Oral melatonin
Describe the cause, appearance and diagnosis of follicular dysplasias
- Heritable breed specific coat abnormalities
- Usually give focal or diffuse symmetrical alopecia affecting dorsum and flanks
- Diagnosis on biopsy
What colours and breeds is colour dilution alopecia usually associated with?
- Blue (dilute blck) or fawn (dilute brown) coat colours
- Esp. Doberman, Dachshun, Yorkie, whippet, Greyhound
What is colour dilution alopecia often associated with?
Often secondary bacterial folliculitis
Describe the occurrence and appearance of colour dilution alopecia dystrophic change
- Dilute colour hair only
- Large melanin granules and abnormally weakened hair
- May lead to shaft fracture and alopecia
Briefly outline black hair follicular dysplasia
- Bi-coloured/tri-coloured puppies
- Melanin clumping on trichograms, defective hair shafts lead to fracture
Compare alopecia in cats and dogs
- Cats similar to dogs
- In cats, incidence of dermatophytosis higher and pyoderma lower
Outline the investigation of alopecia in cats
- Dermatophytosis top differential
- Perform skin scrapes for demodicosis and investigations for dermatophytosis (trichograms, fungal culture, Wood’s lamp)
- If no diagnosis based on these, biopsy
Outline the significance of feline symmetrical alopecia
- Is one of the 4 common cutaneous reaction patterns of cats
- Total/partial acquired hair-loss
- No other gross skin abnormalities
- often symmetrical
- Can be caused by many diseases, need systematic investigations to find primary cause
