Lecture 7. Alopecia-diagnostic Approach

7/24/2019 Lecture 7. Alopecia-diagnostic Approach

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Alopecia- diagnostic approach

Alopecia is defined as a partial or complete absence of hair in areas where hair is normally

present. It may be localised (well-circumscribed alopecia) or affect the whole coat (diffuse or

generalised alopecia).Hair loss may result from a hair schaft lesion, from a disorder of the hair-producing apparatus,

the hair follicle , or from a disorder affecting hair cycle regulation.

There are many causes of alopecia, hence the variety of aetiological, clinical and

histopathological classification schemes, all of which can be useful.

Alopecia may therefore be hereditary or acuired, traumatic (mechanical) or non!traumatic,

hormonal or non!hormonal.

"epending on clinical presentation, alopecia can also be locali#ed, regional (facial, truncal,

limb), multifocal or generali#ed.

Histopathological classification is very helpful and can be used to distinguish different types

of alopecia according to the presence of follicular dysplasia, melanin distribution disorders or

inflammation.

H$%$"ITA%& A'$*IA

Dystrophy or absence of hair follicles

Hereditary hypotrichosis

Canine primary seborea

Abnormalities in the hair shaft structure

Folicular dysplasia

Color dilution alopecia

Black hair folicular dysplasia

Pattern alopecia, Reccurent flank alopecia

Hereditary hypotrichosis

*ongenital hypotrichosis and alopecia are characterised by the absence of hair or

presence of rudimentary hair at birth or during the first month of life.

Canine primary seborrhea

*anine primary seborrhea is a hereditary disorder of +eratini#ation.

* initially appear during puppyhood and may be mild at first but worsen with age.

* may include a dull, dry, lusterless hair coat, ecessive scaling (dandruff), scaly and

crusty seborrheic patches and plaues, and greasy malodorous s+in. eratinocytes are epitelial cells. They undergo a specific differentiation process called

+eratinisation

"uring this differentiation , +eratinocyte morphology changes from small and round in

the basal layer to large, anuclear in the horny layer.

eratinocytes are arranged in the epidermis in continuous layers. /rom the base to the

surface, these are the basal layer, spinous layer, granular layer and horny layer.

This differenciation process ta+es 00 days in 1eagles.

2ost of the body is involved to some degree, with interdigital areas, perineum, face,

aillae, ventral nec+, abdomen and s+in folds usually most severely affected.

ruritus is mild to intense and ceruminous otitis eterna is common.

econdary s+in and ear infections with bacteria andMalasseziaare often present.


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Follicular dysplasia

3 /ollicular dysplasias are a group of dermatoses characterised by a structural hair

follicle abnormality and resulting alopecia. It is important to +now about folliculardysplasias, as they enter into the differential diagnosis of all the endocrine alopecias.

A genetic causes has been proven in some cases and strongly suspected in others.

Aetiopathogenesis is largely un+nown and it is often difficult to distinguish between

these conditions.

"ermatological signs start in young dogs and progress slowly. There

is considerable breed variation

3 In the Siberian Husky and Malamute. /" usually affected several puppies in the same

litter.ne puppies reach three months of age, hairs on the trun+ become reddish,

falling out gradually over subseuent years. The head anf limbs are usually unaffected.

3 The Irish water spanielalopecia stars between two and four years of age, mainly on

the nec+, dorsolumbar region and tail before spreding to the trun+.

Color-dilution alopecia black hair follicular dysplasia!

*olor-dilution alopecia is the most common genodermatosis in the dog and yet, under-

diagnosed in certain breeds (&T).

*"A-has been reported in dogs with blue coats, mainly the "obermann but also in &T, 4reat

"ane, alu+i, "achshund.

The aetiopathogenesis remains poorly understood. ne of the most plausible eplanations

involves a primary hair follicle dysfunction. The presence of follicular lesions (atrophy,

dysplastic lesions) is suggestive of hair follicle dysfunction. Abnormal melanosome transfer

to +eratinocytes is also suspected in the "oberman. 2elatonin stimulating hormone

deficiency is also seen.

"ermatological signs of *"A usually starts between 5 months and 6 years of age. They

include progressive hypotrichosis and etensive alopecia of color-dilute regions, mainly on

the trun+.The head and limbs are often spared or affected much later.

After de"eloping o"er se"eral years , alopecia may in"ol"e the #hole trunk$

Pattern alopecia and recurrent flank alopecia

These are non-inflammatory alopecias.

attern alopecia is a common dermatois with no +nown aetiology. It is probably agenodermatosis.

*linical signs7 alopecia of the base of the conve pinnae, ventral nec+, thora, abdomen and

caudal thighs. It starts at around 8 months of age, progressing gradually over the following

year but remaining locali#ed, it is seen mainly in "achshunds but also in inchers, 9hippets,

1oers:

It has been reported in A2$%I*A; 9ater spaniel and ortuguese water dog. Alopecia starts

at around < months of age, on the ventral nec+, caudal thighs and tail.

It is interesting to note that in the Irish 9ater paniel, alopecia of the tail and ventral nec+ are

listed as breed criteria.

Reccurent flank alopecia


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%/A was described about => years ago. It has many alternative names including

seasonal flan+ alopecia, idiopathic cyclical flan+ alopecia, cyclical follicular dysplasia.

However, none of these titles fits perfectly. In some cases, there is no recurrence and in rare

cases, alopecia permanent.

The increased incidence in certain breeds (1oer, $nglish 1ulldog).

n the other hand ;ordic breeds, 4erman shepherd "og and *oc+er spaniels appear to beunaffected.

The aetiology is un+nown but episodic folli+ular dysfunction is suspected. The recurrent,

seasonal nature of lesions suggests the influence of photoperiod. 2elatonin and prolactin from

the pituitary gland may or may not be involved in the pathogenesis but these two photo-

dependent hormones are certainly involved in hair growth.

"ermatological signs7 alopecia starting on the flan+s, hair regrowth some months later.

Alopecia-bilateral, but often unilateral, non-inflammatory. It has well-defined borders, s+in is

often hyperpigmented.

Alopecia is seen on the lateral pinnae, bridge of the nose and caudal thighs. These locations

are similar to those seen in pattern alopecia, which is certainly not cyclical.

9hen hair regrows, the new coat is normal density but occasionally dar+er in colour than theoriginal. The degree and duration of the alopecia may be similar each year or may increase.

%arely , alopecia becomes permanent after several episodes.

%ebaceous adenitis

3 ebaceous adenitis is a poorly understood, destructive, inflammatory disease of

sebaceous glands.

3 It is uncommon in dogs, with the highest incidence reported in young adult to middle-

aged tandard oodles, hungarian vi#slas, A+itas and amoyeds.

3 An autosomal recessive mode of inheritance is suspected in oodles and A+itas.

3 2ild to severe scaling most often involves the dorsum of the bac+ and nec+, top of the

head, face, ears and tail.

3 The s+in disease may remain locali#ed , become multifocal, or be generali#ed over the

trun+.

3 ruritus is not usually seen unless there is a secondary bacterial or 2alasse#ia

infection, which are common.

3 Any secondary bacterial or 2alasse#ia infections should be treated with appropriate

systemic medications.

3 $ssencial fatty acids, rednisone, vitamine A.

3 The prognosis is variable, depending on disease severity.

&pidermal Dysplasia of 'est Highland 'hite (erriers

3 This is a severe chronic dermatosis characterised by pruritus, seborrhea and

lichenification, it ossurs in 9est Highland 9hite terriers.

3 This disorder is presumed by many dermatologists to be an inherited disorder of

+eratini#ation in which a dysplastic epidermis is predisposed to secondary 2alasse#ia

infection.

3 The development of greasy hair coat is followed by mild to moderate pruritus of the

face, ears, limbs, feet and ventrum.

3 9ith chronicity, the pruritus becomes intense, and widespread areas of pyoderma,

3 alopecia,

3 scaling,3 crusting,


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3 lichenification and

hyperpigmentation.

Ac)uired alopecia

3 (raumatic

3 ruritic dermatoses

3 hysical and chemical assault

3 *on-traumatic

3 $ndocrinopathy

3 Telogen dysplasia

3 ;utritional alopecia

3 /olliculitis

3 erifoliculitis

3 -Leismania

3 - Sebaceous adenitis

3 - Alopecia areata

3 Tumors3 -Epiteliotropic lymphoma

3 "eep pyoderma

3 "ermatomyositis

Canine %cabies

3 arcoptic mange is a contagious parasitic s+in condition caused by the mite, arcoptes

scabiei var. *anis.

2alasse#ia pachydermatis is a yeast that is normally found in low numbers in the eternal ear

canals, in perioral areas, in perianal regions and in moist s+in folds.

3 2alasse#ia overgrowth is almost always associated with an underlying cause, such as

atopy,

3 food allergy,

3 endocrinopathy,

3 +eratini#ation disorder,

3 metabolic disease or

3 prolonged therapy with corticosteroids.

Dermatophytosis

3 The disease is #oonotic

3 "ermatophytosis is an infection of hair coat and stratum corneum caused by

+eratinophilic fungi7

3 Microsporumand Trichophyton

3 It occurs commonly in dogs and cats, with highest incidence reported in +ittens,

puppies, immunossuppresed animals and long-haird cats.

3 +in involvement may be lo+ali#ed, multifocal, or generali#ed.

P+(RA.A(/C D&R.A(/(/% H(-%P(!

3 It is an acute and rapidly developing surface bacterial s+in infection that occurssecondary to self-inflicted trauma.


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3 A lesion is created when the animal lic+s, chews, scratches, or rubs a focal area on its

body in response to a pruritic or painful stimulus.

3 It is usually a seasonal, problem that becomes more common when the weather is hot

and humid.

3 /leas are the most common initiating stimulus.

3 yotraumatic dermatitis is common in dogs, especially in thic+-coated, long-hairedbreeds.

3 yotraumatic dermatitis is an acutely pruritic, rapidly enlarging area of erythema,

alopecia and weepy, eroded s+in with well-demarcated margins.

3 'esions are usually single, but they may be multiple and are often painful.

3 They occur most freuently on the trun+, tail base, lateral thigh, nec+, and face.

3 The prognosis is good if the underlying cause can be corrected or controlled.

3 Aggressive flea control should be provided.

3 The lesion should be clipped and cleaned.

3 If pruritus is mild, a topical analgesic (e.g.lidocaine) or corticosteroid-containing

cream or solution should also be applied every ? to =0 hours for > to =@ days.

3 If pruritus is severe, prednisone @,> to =,@mg!+g p.o. should be administered every 05hours for > to =@ days.

3 If the central lesion is surrounded by papules or pustules, systemic antibiotic therapy

should also be instituted and continued for 6 to 5 wee+s.

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Lecture 7. Alopecia-diagnostic Approach