3. Skin diseases - allopathic

What is alopecia?

Partial or complete absence of hair where normally present

Is alopecia a disease or a symptom?

A symptom

What are the two main classifications of alopecia based on distribution?

Localised (well-circumscribed) and diffuse or generalised

Name some primary causes of alopecia.

1. Neoplasia

2. Bacterial folliculitis

3. Demodicosis

4. Genetic factors (e.g., hairless breeds, congenital hypotrichosis, colour dilution alopecia)

5. Inflammatory conditions (auto-immune diseases like pemphigus, dermatophytosis)

Name some secondary causes of alopecia.

1. Stress

2. Nutritional deficiencies (malnutrition, vitamin A deficiency, fatty acid deficiency)

3. Endocrine disorders (hypothyroidism, hyperadrenocorticism, hyposomatotropism, sex hormone imbalances like hyperestrogenism and Sertoli cell tumours)

What are some ways alopecia can be classified?

1. Hereditary or acquired

2. Traumatic (mechanical) or non-traumatic

3. Hormonal or non-hormonal

What are examples of hereditary alopecia?

1. Hereditary hypotrichosis

2. Canine primary seborrhoea

3. Follicular dysplasia

4. Canine recurrent flank alopecia

5. Sebaceous adenitis

6. Epidermal dysplasia of West Highland White Terriers

What structures may be affected by genetics causing alopecia?

1. Hair follicles

2. Hair shaft structure

What are some examples of hereditary alopecia regarding dystrophy or absence of hair follicles?

1. Hereditary hypotrichosis

2. Canine primary seborrhoea

What is hereditary hypotrichosis?

Congenital hair follicle dystrophy causing reduced hair, common in hairless breeds (Mexican hairless, Chinese crested)

What are some clinical signs of hereditary hypotrichosis?

Hair loss or rudimentary hair at birth, comedones, mild pyoderma or seborrhoea

How is hereditary hypotrichosis diagnosed?

History, examination, and genetic testing

What is the treatment for hereditary hypotrichosis?

There is no cure; treatment focuses on managing secondary infections with antiseborrheic shampoos

How can hereditary hypotrichosis be prevented?

Selective breeding and gene screening

What is canine primary seborrhoea?

A hereditary keratinization disorder seen in breeds like Cocker Spaniels and Basset Hounds

What are some clinical signs of canine primary seborrhea?

Dry, scaly, greasy skin, pruritus, and ear infections

How is canine primary seborrhea diagnosed?

Examination, skin scrapings, and cultures

What is the treatment for canine primary seborrhea?

Medicated shampoos and antibiotics for infections

How can canine primary seborrhea be prevented?

Selective breeding

What is follicular dysplasia?

A group of dermatoses characterised by structural hair follicle abnormality and resulting alopecia

What breeds are commonly affected by follicular dysplasia?

Huskies, Malamutes, and other breeds

What are some clinical signs of follicular dysplasia?

Gradual hair loss, dry skin, and secondary infections

Is there a treatment for follicular dysplasia?

No

How can follicular dysplasia be prevented?

Selective breeding

Name some types of follicular dysplasia.

1. Cyclic follicular dysplasia: caused by amount of daylight exposure to dog

2. Colour dilution dysplasia: caused by macro melanosomes of hair shaft, leading to brittleness & fracture. Predisposed breeds have a blue or fawn coat: Yorkshire Terriers, Chihuahuas, Salukis

3. Black hair follicular dysplasia: genetic defect affecting formation of the hair shaft & transfer of melanin. Causes hair loss specific to black hairs. Breeds- bi or tri-coloured coats.

4. Follicular lipidosis of Rottweilers: rare, breed specific condition - affects tan areas of animal’s face & legs causing localised alopecia.

What is canine recurrent flank alopecia?

A seasonally recurring follicular dysplasia. Common in boxers, bulldogs, schnauzers.

What is a possible cause of canine recurrent flank alopecia?

Photoperiod control of melatonin and prolactin secretion

When does seasonal hair loss typically occur in canine recurrent flank alopecia in the northern hemisphere?

November–March

What are some clinical signs of canine recurrent flank alopecia?

Symmetrical, non-pruritic alopecia on the flanks

What is the treatment for canine recurrent flank alopecia?

None

How can canine recurrent flank alopecia be managed?

Minimising stressors and managing light exposure

What is sebaceous adenitis?

A poorly understood, destructive, inflammatory disease of sebaceous glands

What breeds have the highest incidence of sebaceous adenitis?

Standard Poodles, Hungarian Vizslas, Akitas, and Samoyeds

What are some clinical signs of sebaceous adenitis?

Scaling, alopecia involving the dorsum of the back and neck, top of the head, face, ears, and tail, and pruritus with secondary infections

How is sebaceous adenitis diagnosed?

Biopsy and trichogram

What is the treatment for sebaceous adenitis?

Cyclosporin, essential fatty acids, retinoids, and medicated shampoos

What is epidermal dysplasia of West Highland White Terriers?

A severe chronic dermatosis characterised by pruritus, seborrhea, and lichenification

What is a possible cause of epidermal dysplasia of West Highland White Terriers?

A hereditary exaggerated response to Malassezia infection or hypersensitivity

What are some clinical signs of epidermal dysplasia of West Highland White Terriers?

6-12 months old. Greasy hair coat (seborrhoea), severe pruritus, erythema, alopecia, scaling, crusting, lichenification, and hyperpigmentation of the face, feet, limbs, and ventrum, and otitis externa

How is epidermal dysplasia of West Highland White Terriers diagnosed?

Cytology (Malassezia) and biopsy

What is the treatment for epidermal dysplasia of West Highland White Terriers?

Treating underlying allergies and secondary pyoderma with appropriate systemic antibiotics and secondary Malassezia with ketoconazole

Is acquired alopecia more or less common than hereditary alopecia?

More common

What are types of acquired alopecia?

1. Functional

2. Structural

3. Traumatic

What is functional alopecia?

Alopecia caused by alteration of the hair cycling, often due to endocrinopathies

What are some examples of endocrinopathies that can cause functional alopecia?

1. Cushing’s: Bilateral alopecia found throughout the body except on head or limbs.

2. Hypothyroidism: bilateral symmetrical alopecia w/ dull & brittle hair coat, rat tail.

3. Hypoestrogenism: bilateral symmetrical alopecia of rump, flanks, earlobes, hyperpigmentation of linea alba, generalised dermatosis - except head & limb.

4. Oestrogen-producing Sertoli cell testicular tumour

How is functional alopecia diagnosed?

By a process of elimination to identify the underlying endocrinopathy

What is structural alopecia?

Loss of normal follicular structure causing non-symmetrically localised/non-regulated alopecia with inflammation. Refers to damage to the hair shaft due to external factors rather than inherent genetic defects

What is the most common cause of structural alopecia?

Infectious folliculitis by Staphylococcus folliculitis, demodicosis, and dermatophytosis

What are some clinical signs of structural alopecia?

Localised or generalised hair loss or thinning, pruritus, dry/brittle hair, and possible secondary infections

How is structural alopecia diagnosed?

Skin scrapings, cytology, smears, tape preparations, fungal or bacterial cultures, microscopy of hair (trichogram), and CBC

What is traumatic alopecia?

Alopecia caused by fracture of the hair shaft

What are some causes of traumatic alopecia?

1. Sarcoptic mange

2. Hypersensitivity

3. Malassezia

4. Pyotraumatic dermatitis (hot spot)

5. Recurrent otitis externa

6. Skin fold dermatitis (intertrigo)

What are clinical signs of traumatic alopecia?

Pruritus, broken hair - short stubbles of hair

How is traumatic alopecia diagnosed?

Skin scrapings, cytology, smears, tape preparations, fungal or bacterial cultures, microscopy of hair (trichogram), and CBC

What is the typical presentation of dermatophytosis?

Localised round alopetic lesions

Where does alopecia often start in demodicosis?

Around the eyes

What is the main clinical sign of traumatic alopecia?

Broken hairs/short stubbles