Approach to Alopecia NOTES 2024 PDF

APPROACH TO ALOPECIA MIRINDA VAN SCHOOR Approach to Alopecia: Learning Outcomes Define the term “Alopecia”. Describe the normal hair growth cycle. Identify the pathological process associated with abnormal hair growth: follicular absence, dysplasia, cyclical abnormalities, follicular...

APPROACH TO ALOPECIA MIRINDA VAN SCHOOR Approach to Alopecia: Learning Outcomes Define the term “Alopecia”. Describe the normal hair growth cycle. Identify the pathological process associated with abnormal hair growth: follicular absence, dysplasia, cyclical abnormalities, follicular insult. Identify cases of hair loss. Recognise distribution patterns of alopecia and their significance. Describe the various diagnostic procedures to determine aetiology: history, examination, laboratory. Discuss approaches to appropriate management. #universityofsurrey 2 Alopecia: What is alopecia? A lack of hair in normally haired areas. Distribution: Generalised, multifocal or localised. #universityofsurrey 3 Hair growth cycle Revisit anatomy and physiology lectures Self-study Normal hair growth – Refer to VMS 1004 Self-study/revision Hair is formed by the hair follicle. Follicles may be: Simple: single hair shafts exits the infundibulum. Compound: multiple hair shafts exit the infundibulum. Hair shafts may be: Primary: larger Secondary: smaller undercoat Horses and cattle have only simple follicles; dogs and cats have simple and compound. Horses have only primary hairs; dogs and cats have primary and secondary hairs. Formation is cyclical. #universityofsurrey 5 Hair growth cycle – Refer to VMS 1004 Self-study/revision The cycle is controlled by intrinsic and extrinsic factors: Intrinsic: cellular level within the follicle Extrinsic: Environmental – photoperiod; temperature. Hormones – melatonin; prolactin; sex hormones; thyroxine; glucocorticoids; growth hormone. Nutrition General health Genetic Hair is continuously growing and shedding in a mosaic pattern. #universityofsurrey 6 Normal hair growth Refer to VMS 1004 Self-study/revision Cycle: Anagen: Growth phase Catagen: Transition phase Telogen: Resting phase Pictures: A: Fully functional hair follicle: ‘Anagen phase’ B: Follicle begins to atrophy: ‘Early Catagen phase’ C: Further atrophy of follicle: ‘Late Catagen phase’ D: Atrophied follicle: ‘Telogen phase’ E: New matrix established and new hair begin to grow: ‘Early Anagen phase’ (exogen) #universityofsurrey 7 Pathological processes Pathogenesis of alopecia Only one of two things can be happening: Failure of follicle to grow hair Loss of existing hair 1. Lack of follicles 1. Hair falling out of follicles 2. Follicle Dysplasia 2. Breaking of hair 3. Abnormal follicle cycle 4. Damaged follicles #universityofsurrey 9 Lack of follicles Lack of follicles Examples: Congenital Hypotrichosis: Sphinx cat, Devon Rex Alopecia Universalis – sphinx Hereditary hypotrichosis: Devon Rex Canine Ectodermal Dysplasia (Chinese Crested Dog) Note: hairlessness is an incomplete dominant trait. The hairless gene has a prenatal lethal effect when homozygous. Zygotes that have two copies of the hairless allele will never develop into puppies. Hairless Chinese crested Powderpuff Chinese crested #universityofsurrey 11 Follicle Dysplasia Follicle Dysplasia A group of often ill-defined alopecia disorders that are frequently linked to coat colouring Follicle dysfunction due to structural abnormality Genetic condition – often breed related May occur early or can occur later in life as follicles atrophy Several types Always associated with abnormalities of the hair shaft #universityofsurrey 13 Follicle Dysplasia Canine examples: 1. Structural follicle dysplasia 2. Follicular lipidosis 3. Colour dilution alopecia 4. Black hair follicle dysplasia 5. Cyclic follicular dysplasia/ seasonal alopecia #universityofsurrey 14 Follicle Dysplasia Structural follicular dysplasia Breeds: Irish water spaniel Portuguese waterdog Doberman Weimeraner Disorder of follicle development that affects young to middle aged dogs Weak hairs break easily – focal or diffuse symmetrical alopecia Seen caudal lumbar – progressively extends over trunk #universityofsurrey 15 Follicle Dysplasia Colour dilution alopecia Blue/fawn coated breeds (dilution of black or brown): Doberman, whippet, saluki, Great Dane Melanocytes dysfunction in the follicle Coat normal at birth – start losing hair at 6 months to 2 years Clumping of pigment causes defect in the hair and hair eventually breaks Skin infections can occur Black hair follicular dysplasia Rare Occurs in black haired areas Associated with defective pigmentation and formation of hair Puppies normal at birth but lose hair at around 1 month of age Similar to colour dilution #universityofsurrey 16 Follicle Dysplasia Cyclical follicular dysplasia/ seasonal alopecia/ recurrent flank alopecia Often in autumn or spring 2-4 years of age Bilateral flank alopecia Hair can regrow Melatonin administration may help Melatonin is a hormone produced by the pineal gland – helps to regulate hormones and the body’s circadian rhythm May be relationship between melatonin, sunlight and cyclical dysplasia May try prophylactic use Genetic predisposition: boxer, bulldog, Airedale, schnauzers #universityofsurrey 17 Miscellaneous Atrophic follicular pattern baldness Characterised by miniaturisation of follicles Associated with short coated breeds – possibly as result of selecting for fine, delicate coats Different patterns – ears; ventral abdomen and chest; thighs Often starts late puberty Dachshund, Chihuahua, sight hounds May progress to complete alopecia – skin may become hyperpigmented over time #universityofsurrey 18 Miscellaneous Idiopathic bald thigh syndrome of Greyhounds and other sighthounds Specific to sighthounds (Image: Shakesville: Daily Dose of Cute) Caused by structural hair shaft defects Associated with downregulation of genes regulating essential proteins for hair shaft formation Used to be considered a follicular pattern alopecia but no hyperpigmentation present – now considered a separate condition Usually, young adults Complex mode of inheritance #universityofsurrey 19 Miscellaneous Feline examples: Pre auricular alopecia Pinnal alopecia #universityofsurrey 20 Abnormal Follicle Cycle Abnormal follicle cycle Due to: anagen inhibition, catagen induction and/or prolongation of telogen Characterised by: Miniaturisation of hair shafts Persistence of telogen follicles Increase in hairless telogen follicles Causes: Endocrine disease Alopecia X Systemic disease Drugs Telogen effluvium (defluxion) Post clipping #universityofsurrey 22 Abnormal follicle cycle Endocrine disease Several hormones involved in maintenance of healthy follicle and hair growth Thyroxine, corticosteroids, oestrogen, testosterone, growth hormone Hairs arrested in telogen (rest) phase, are shed and do not regrow Endocrine diseases resulting in alopecia include: Hypothyroidism Hyperadrenocorticism Hyperoestrogenism/ testosterone Pituitary dwarfism #universityofsurrey 23 Abnormal follicle cycle Hyperoestrogenism Male dogs with Sertoli cell tumours castrate Bitches with cystic ovaries spay Pituitary dwarfism Inadequate secretion of growth hormone Retardation of growth and progressive hair loss Genetic predisposition in GSD’s Treatment: growth hormone £££££ Progestogens and thyroxine, but side effects #universityofsurrey 24 Abnormal follicle cycle Alopecia X (dogs) Hair cycle arrest Primary hairs affected first – soft, downy secondary hairs remain Gradual hair loss over trunk and caudal thighs Sparing head and forelimbs Thought to be adrenal sex hormone imbalance Similarity with hyperoestrogenism Breed predisposition Poodle; Pomeranian (and arctic breeds) 2-5 years of age Treatment: thyroxine, trilostane, melatonin, castration, deslorelin – side effects Aesthetic concern only #universityofsurrey 25 Abnormal follicle cycle Systemic disease Many systemic diseases will interrupt the hair growth cycle: Hepatic disease; end stage renal disease; pancreatic disease; neoplasia (paraneoplastic syndrome) Drug therapy Cytotoxic drugs Cancer treatments Steroids Prolong the telogen phase – hair shed and not replaced May see focal lesions after topical use of corticosteroids #universityofsurrey 26 Abnormal follicle cycle Telogen effluvium (defluvium/defluxion) Stressful event can cause abrupt cessation of hair growth in the anagen phase Surgery; pregnancy; parturition; shock; severe illness Hair follicles become synchronised in the telogen phase 2-3 months after the event, telogen hairs shed – temporary alopecia Post clipping Hair does not regrow immediately Breed related – heavily coated breeds (malamute; husky) Prolonged telogen phase – hairs may be retained for 2 years – if clipped, may take long time to regrow – may take several months to regrow #universityofsurrey 27 Damaged follicles Damage to follicles Infection Immune Mediated Disease Neoplasia Trauma Tail gland hyperplasia Sebaceous glands become enlarged under androgen influence Results in damage to follicle and failure of hair growth ©Vet stream #universityofsurrey 29 Damage to follicles Infections Bacterial – primary or secondary Dermatphilus congolensis (mud fever) Fungal Ringworm Mites demodecosis #universityofsurrey 30 Damage to follicles Immune mediated disease Sebaceous adenitis Autoimmune response against sebaceous glands in hair follicles Genetic predisposition; mostly seen in dogs; rarely in other mammals Young to middle aged dogs Two expressions in dogs Long coated breeds – poodle, Akita, Samoyed – lesions ears, back and flanks Short coated breeds – Viszla – facial lesions and generalised moth-eaten lesions Variety of treatments: Vit A; EFAs; cyclosporine Secondary infections common – bacterial/fungal #universityofsurrey 31 Damage to follicles Immune mediated disease Drug reaction Topical reaction or injection site reaction Hair loss may be immediate or delayed and may not regrow Avoid use of product Note: Seen with some ectoprasiticide “spot ons” Delvosterone (progesterone) for control of season in bitches #universityofsurrey 32 Damage to follicles Neoplasia Occult sarcoids in horses Nutrition Zinc responsive dermatosis in dogs Zn needed for cell replication – important for skin turnover Type I familial form – Husky, Malamute – genetic defect resulting in malabsorption Type II relative insufficiency –diet high in plant origin Trauma Burns – chemical and thermal – BEWARE use of heat pads during surgery Injury #universityofsurrey 33 Damage to follicles Immune mediated disease Autoimmune Alopecia areata Rare Multifocal patchy hair loss Danny W. Scott, in Rebhun's Diseases of Dairy Cattle (Second Edition), 2008 Affects many animals In dogs often symmetrical, affecting face, head and legs Autoantibodies directed against hair follicle proteins Hair regrowth is often spontaneous (one paper cited remission in 60% of cases) – regrowth may be lighter (non-pigmented) Resistant cases usually respond to corticosteroids or cyclosporin #universityofsurrey 34 Loss of existing hair  Loss of existing hair Bald patches – not true alopecia PRURITIS Allergy Atopy; food hypersensitivity; contact; ectoparasites (flea allergy dermatitis, sweet itch) Bacterial Fungal Dermatopytes, yeasts Ectoparasites Fleas; mites (sheep scab – Psoroptes ovis) - NOTIFIABLE Prions “scrapie” – spongiform encephalopathy - NOTIFIABLE #universityofsurrey 36 Loss of existing hair SELF MUTILATION Psychogenic/ behavioural CATS Feline psychogenic alopecia Pain related licking – cystitis/ GI RABBITS Nesting behaviours #universityofsurrey 37  © Vetstream Loss of existing hair Feline psychogenic alopecia Hair loss and/or skin damage resulting from displacement grooming in reaction to stressors which may be emotional or environmental. Diagnosis of exclusion –made when all medical differentials ruled out Since psychogenic alopecia is a multifactorial condition, treatment will need to be tailor made for each case Address associated stressors Increase stability of the emotional and physical environment of the cat Use desensitization and counterconditioning techniques to deal with any underlying fears or phobias relating to specific stimuli. In severe cases psychopharmacology may be needed for example with tricyclic antidepressants or serotonin reuptake inhibitors (SSRIs). Treatment will only be effective in combination with behavioural modification. #universityofsurrey 38 Loss of existing hair Extraneous mutilation Barbering of companions Rabbits; guinea pigs Feather pecking in hens Trauma/friction Horses – rugs Yorkies with ponytails Dermatophytosis Weakens hair with resultant fracture #universityofsurrey 39 Lesion Distribution Diagnosis: Lesion Distribution Sue Phillips #universityofsurrey 41 Diagnostic approach Approach to Diagnosis Minimum database – always be systematic Signalment History Physical examination Dermatological examination Laboratory tests #universityofsurrey 44 Diagnosis - History How long has the condition been present? Is it progressive? Any previous occurrence? If so – is it season related? Any concurrent illness – (vomiting fur balls)? Any stressful incident? Any other animals? If so – are they affected? Grooming? Current medications – steroids/topical preps? Current ectoparasite control? Nutritional status #universityofsurrey 45 Diagnosis: Examination Signalment (Age, Breed, Colour, Sex – all may increase or decrease index of suspicion) Full physical examination - concurrent illness ? Dermatological examination: Distribution? Focal vs generalised/symmetrical vs nonsymmetrical Location - ears, dorsum, groin, flanks? Skin appearance With true alopecia, particularly lack of follicles and follicular dysplasias, the skin may look normal – no papules/pustules/scaling/crusting Complete or partial alopecia? 1o hairs lost but some 2o hairs remaining – suggestive of self trauma/ (AlopeciaX) Entire hair lost or hair broken? ( stubby ) Broken hairs - trauma from mutilation or weak hairs easily broken - dematophytosis #universityofsurrey 46 Diagnosis: Dermatological examination Skin appearance shiny - paraneoplastic alopecia (pancreatic tumour) thin fragile – hyperadrenocorticism seborrhoeic - hypothyroidism, scaling, crusts - auto-immune disease infection neoplasia drug reaction erythema – allergy no lesion - telogen effluvium follicular dysplasia #universityofsurrey 47  Diagnosis: Laboratory tests Trichography (hair plucks) Skin scrapes Trichography, skin Brushings scrapes, biopsy and U/V lamp ( some Microsporum sp fluoresce) hormone assays Strips probably the most Cytology/culture Dermatophyte culture useful in relation to Biopsy diagnosis of Allergy testing/ dietary trials/ response to steroids alopecia Hormone assays (and other blood tests and urine analysis) Cats: FIV, FeLV Ultrasound/ radiographs if neoplasia is suspected Faecal evaluation #universityofsurrey 48 Diagnosis: Laboratory tests #universityofsurrey 49 Diagnosis: Laboratory tests TRICHOGRAPY Broken hair shafts suggest trauma or weak hairs 100% telogen hairs suggests cyclical disruption Anagen hairs indicate actively growing hairs Demodex Increased and abnormal deposits of melanin – colour dilution alopecia Hyphae and spores – dermatophytosis Easy epilation - folliculitis #universityofsurrey 50 Approach to treatment of Alopecia Identify the primary cause Treat primary condition where possible. Address any secondary complications Some true alopecias may be an aesthetic issue only – and may have to be accepted #universityofsurrey 51 Approach to treatment of Alopecia Follicular absence & Follicular dysplasia Cannot do much about it. Melatonin, retinoids, or essential fatty acids (EFAs) may improve condition of the skin Largely aesthetic Some may resolve – recurrent flank alopecia #universityofsurrey 52 Approach to treatment of Alopecia Abnormal cycle Identify and address the primary cause Avoid known drug triggers (drug reactions) Avoid stress triggers (Telogen effluvium) Prognosis dependent on cause Endocrine disorders ongoing and will require control #universityofsurrey 53 Approach to treatment of Alopecia Damage to follicles (Infection, Immune mediated disease, Neoplasia, Nutrition, Trauma) Identify and address the primary cause Prognosis dependent on cause If damage to follicles is severe, permanent alopecia will result #universityofsurrey 54 Approach to treatment of Alopecia Loss of existing hair Identify the cause Identify allergens and avoid/immunotherapy Treat underlying infections/parasites Barbarism –evaluate husbandry manage stressors environmental enrichment Psychopharmacology #universityofsurrey 55 Examples of algorithms – Clinical Veterinary Advisor Canine Feline #universityofsurrey 56 Resources CVPM, S.W., RVT (2021). A Clinical Approach to Alopecia in Cats. [online] Today’s Veterinary Practice. Available at: https://todaysveterinarypractice.com/dermatology/alopecia-diagnosis-cats/ [Accessed 6 Nov. 2023]. Monika Maria Welle (2023). Canine noninflammatory alopecia: An approach to its classification and a diagnostic aid. Veterinary Pathology, 60(6), pp.748– 769. doi:https://doi.org/10.1177/03009858231170295. www.veterinarypracticenews.com. (2021). Diagnosing and treating alopecia in dogs - Veterinary Practice News. [online] Available at: https://www.veterinarypracticenews.com/diagnosing-and-treating-alopecia- in-dogs/. Clinical Veterinary Advisor: Dogs and Cats, 3rd edition. Côté E, ed., Elsevier, St. Louis, Missouri, USA. 2020. ISBN 9780323676755 58