Diseases of the Hair follicles & Adnexa

Question 1

What are the main diseases of the hair follicles & adnexa?

Answer 1

• pustular & nodular dz w/o adnexal destruction
• pustular & nodular dz w/ adnexal destruction
• atrophic dz’s of the adnexa
• dysplastic dzs of the adnexa
• dz’s of the panniculus
• lupoid onychitis (nail dz)

Question 2

What are the main pustular & nodular diseases w/o adnexal destruction?

Answer 2

• dermatophytosis (ringworm)
• superficial bacterial folliculitis

Question 3

Characteristics of superficial bacterial folliculitis

Answer 3

• hair follicles inflamed/infected
• Staphyloccocus pseudointermedius
• Secondary to coexistent dz/ predisposing factors
• Affects humans, dogs, cats, horses

Question 4

Gross lesion of superficial bacterial folliculitis

Answer 4

• transient follicular pustules leading to crusted papules
• Form at hair follicle opening, leaks, then hair follicle forms; less haired areas allow bacteria to get in easier
• alopecia, hyperpigmentation
• inguina & axilla, interdigital webs

Question 5

Characteristics of dermatophytosis

Answer 5

• superficial cutaneous, self-limiting dz caused by Microsporum spp or Trichophyton spp
• Common in calves, horses, cats
• mainly young or immunosuppressed
• colonize keratin only (dead tissue)

Question 6

Histopathological lesion of superficial bacterial folliculitis

Answer 6

• pustules w/i the infundibulum or ostium of superficial hair follicles = folliculitis
• neutrophils in the ostium

Question 7

Predisposing factors to dermatophytosis

Answer 7

• hot, humid environments
• sweat

Question 8

Gross lesion of dermatophytosis

Answer 8

• expanding circular patches of scaling & alopecia or stubbled hair

Question 9

Histopathology of dermatophytosis

Answer 9

• neutrophilic luminal folliculitis
• furunculosis (rupture of hair follicle in end-stage)

Question 10

What are pusular and nodular diseases w/ adnexal destruction?

Aka cause destruction of the hair structure

Answer 10

• Deep bacterial folliculitis & furunculosis (post-grooming furunculosis, acral lick dermatitis, interdigitial furunculosis, callus pyodrma, canine acne)
• feline acne
• canine demodicosis
• sebaceous adenitis

Question 11

Deep bacterial folliculitis & furunculosis characteristics

Answer 11

• GSD, cats
• Traumatic furunculosis –> acral lick, painful
• Self-inflicted
• furunculosis: traumatically released hair fragments & remnants of follicular keratin (FB rxn)

Question 12

What organisms are implicated in deep bacterial folliculitis & furunculosis?

Answer 12

• Staphyloccoccus pseudointermedius
• Proteus sp
• Pseudomonas sp
• E. coli

Question 13

Predisposing factors to deep bacterial folliculitis & furunculosis

Answer 13

• generalised demodicosis
• hyperadrenocorticism (Cushing’s)
• widespread actinic dz
• immunologic defects

Question 14

Gross lesion of deep bacterial folliculitis & furunculosis

Answer 14

• pustules, nodules, fistulas, haemorrhagic crusts, erosions, ulcers, alopecia, hyperpigmentation & lichenification
• fistula common
• hair follicle epithelium hyperplasia

Question 15

histopathological lesion of deep bacterial folliculitis & furunculosis

Answer 15

• haemorrhagic bullae w/ furunculosis
• +/- ulceration, neutrophils w/i hair follicle, follicle rupture, pyogranulomatous inflammation around keratin & hair shaft fragments w/i dermis

Question 16

Canine acne

Answer 16

• muzzle folliculitis & furunculosis
• deep folliculitis & furunculosis affecting chin
• unknown cause
• young dogs, short hair
• Papules –> pustules –> rupture –> nodules –> fistulae drain –> alopecia
• Histo: pyogranulomatous folliculitis & furunculosis

Question 17

Feline Acne

Answer 17

• comedo formation & secondary inflammation on chin/skin adj to lips
• No age association
• Common cause: immunosuppression
• poor grooming habits & defects in follicular keratinisation
• opportunists (Staph, Strep, P. multocida)
• Histo: comedones, rupture, furunculosis, granulomatous

Question 18

Canine Demodicosis

Answer 18

• non-contagious
• overpopulation of Demodex spp
• Juvi onset & adult onset forms
• Localised (self-limiting) or generalised (life-threatening)
• familial - young dogs CMI defect
• Isoxalines for txt
• Generalised secondary bacterial infections –> sepsis –> life-threatening
• cell-mediated immune defect
• Adult onset assoc’d w/ systemic dz (neoplasia, endocrinopathy, immunosuppressive therapy)

Question 19

Demodicosis can cause…

Histopath features

Answer 19

• folliculitis & perifolliculitis
• eosinophils as perivascular infiltrate
• mites in hair follicles
• follicular hyperkeratosis
• no inflammation allow mvmt of organism
• lymphocytes/plasma cells

Question 20

sebaceous adenitis

Answer 20

• dogs/cats
• Cause: unknown; genetic in poodles/akitas
• inflammatory destruction of sebaceous glands or cornification abnormality –> sloughing –> blockage –> leakage sebum –> inflammation
• frond-shaped keratin

Question 21

Gross sebaceous adenitis

Answer 21

• adherent scaling forming follicular casts or fronds
• coat qlty: dull, dry, brittle, broken hairs
• bilaterally symmetric (dorsal trunk, temporal region, face, pinnae) striking alopecia & adherent scale on tail

Question 22

Histopath of sebaceous adenitis

Answer 22

• absence of sebaceous glands w/ limited inflammation
• inflammation at one side of hair follicle - lymphocytic & granulomatous
• hyperkeratosis

Question 23

Atrophic diseases of the adnexa

Answer 23

• hypothyroidism
• hyperglucocorticoidism
• hypoesterogenism
• post-clipping alopecia
• feline psychogenic alopecia

Question 24

Atrophic dermatosis

Answer 24

• noninflammatory dz of hair follicle
• can pull hair out
• endocrinopathies: bilateral symmetric alopecia; hyperpigmentation; hair coat dry, brittle, dull, easily epilated; secondary pyoderma & seborrhoea common

Question 25

Histopath of atrophic dermatosis

Answer 25

* ortho/parakeratotic hyperkeratosis * follicular keratosis * decreased no. of hair shafts in follicular infundibular * telogen hairs & follicular atrophy * epidermal hypermelanosis * dermal & sebaceous gland atrophy * epidermis thin, thickened stratum corneum * arrector muscles large b/c everything else is small * increased pigmentation * collagen in dermis atrophied

Question 26

Hypothyroidism

Answer 26

* most common endocrine SKIN disorder * middle-aged dogs (other species assoc'd w/ iodine def & goitre) * primary hypothyroidism (lymphocytic thyroiditis) * Predisposed breeds: Dobie, G. Retriever, Boxer, G. Dane, I. setter * More spec changes: myxoedema, dermal thickening, prominent hypertrophied vacuolated arrector pili muscles

Question 27

Hyperadrenocorcitism

Answer 27

* pituitary tumour (bilat adrenal cortical hyperplasia) or neoplasm of adrenal cortex * Iatrogenic hyperglucocorticism * over the withers area * common in dogs * primarily skin of trunk affected * pendulous abd, **decreased skin elasticity**, slow wound healing * **calcinosis cutis**

Question 28

Hyperoestrogenism

Answer 28

* middle aged-older intact dogs * Causes: urinary incontinence or O cream; Fxnl testicular neoplasm (sertoli cell tumour); iatrogenic oestrogen admin * Predisposed: Boxer, Shetland sheepdog, Cairn Terrier, Pekingnese, Collie, Weimaraner * Signs: Gynecomastia, prostatomegaly, enlarged vulva; mammary enlargement, hind-end extending forwards * Derm: symmetrical hypotrichosis originates at perineum & genitals

Question 29

Post-clipping alopecia

Answer 29

* lack of hair regrowth following close clipping * Breeds: plush-coats * cause unknown (thermoreg locally) * vasc constriction at follicle prevents regrowth * 6-12 mos before return of hair coat * new coat may be darker * **Caution in show animals** * histo: hairs in quiescent telogen phase

Question 30

Feline Psychogenic Alopecia

Answer 30

* self-traumatic hair removal * obsessive/compulsive disorder or anxiety neurosis * Dx of exclusion * well-demarcated, partial or almost complete alopecia over lateral trunk, caudal & medial thighs, abd, dorsal forelegs (inguinal region/hind legs most common) * Excess hair present in faeces = huge hint * histo = normal or mild inflammation

Question 31

Dysplastic diseases of adnexa

Answer 31

* colour dilution alopecia * hypotrichosis * cyclic flank alopecia

Question 32

Colour dilution alopecia

Answer 32

* dogs, cats, horses (blue/denim or fawn colours) * folliclar dysplasia leading to poor hair coat qlty & variable alopecia * Genetic: Dobie, Doxie, G. Dane, etc * hairs contain larger, abnormal pigment granules due to abnormalities in melanin transfer & storage * dry, dull, brittle, poor qlty haircoat * hair regrowth poor --> progressive, partial, patchy (motheaten) alpecia & broken stubble * hyperpigmentation chronic *** poor hair coat, not histologically normal * pigment in hair shaft = abnromal, follicles = normal**

Question 33

Histo of colour dilution alopecia

Answer 33

* macromelanosomes * follicular dysplasia * hair fractures b/c contain large aggregates of melanin

Question 34

Congenital Hypotrichosis

Answer 34

* variable degrees of hairlessness * all domestic species * commonly assoc'd w/ other defects: dental, adnexal = Ectodermal dysplasia * Dysplasia of the hair follicles, more coarse hair, grow more hair as they age

Question 35

Non-Genetic Hypotrichosis

Answer 35

* Iodine def in piglets, lambs, calves * Goitre & hypotrichosis * intrauterine infection, BVDV, Classical Swine fever, Anything affecting thyroid, chronic mucosal dz * really sick dog - 6 mos later, loses all hair, alopecia, due to stressful event

Question 36

Diseases of the panniculus

Answer 36

* Vx-assoc'd panniculitis * traumatic panniculitis * idiopathic sterile nodular panniculitis * feline panosteitis (rare) * pancreatic panniculitis (rare)

Question 37

Injection/Vx-Assoc'd Panniculitis

Answer 37

* Post-rabies (relatively common) * inflammation centred on BV's in area Vx was given * avoid further Vx if occurs * ischaemia

Question 38

Gross lesion of Vx-assoc'd panniculitis

Answer 38

* focal alopecia - minimal gross inflammation, 2-3 mos post-vx * idiosyncratic immunological rxn to rabies antigen targeting bvs * long-haired or curly haired predisposed

Question 39

Histopath of Vx-assoc'd panniculitis

Answer 39

* ichaemic lesions of dermis (pallor & atrophy) * accumulations of lymphocytes, fewer histiocytes, occasional plasma cells in lower dermis & panniculus surrounding bvs +/- amorphous basophilic foreign material

Question 40

Traumatic panniculitis

Answer 40

* focal ischaemia caused by blunt trauma, chronic pressure, or decreased blood supply * more common in obese cats/dogs

Question 41

Gross lesion of traumatic panniculitis

Answer 41

* focal, firm SQ nodule, predominantly on trunk, esp dorsally over dorsal spinous pocesses & ventral sternum

Question 42

Histopath of traumatic panniculitis

Answer 42

* large, central focus of loular fat necrosis * ruptured adipocytes form large, cystic spaces * foamy macrophages containing lipid debris * +/- haemorrhage or haemosiderosis * marginal fibrosis * Walling-off fibrosis = ideal

Question 43

Idiopathic sterile nodular panniculitis

Answer 43

* Doxies * Gross: multiple firm to fluctuant, deep-seated nodules; larger nodules ulcerate or fistulate; chronic lesions may be depressed, irregularly firm & nodular on palpation * Systemic signs: fever, anorexia, general malaise * **present in older dogs; differentiate from puppy strangles** * Confirm culture & pancreatitis = Neg ensures sterile * Immunosuppressant or sterile txt

Question 44

Histopath of idiopathic sterile nodular panniculitis

Answer 44

* +/- ulceration * deep dermis inflammed * neutrophils & macrophages * granulomas * necrotic adipocytes

Question 45

Lupoid Onychitis

Answer 45

* canine syndrome * separation of claw from clawbed, sloughing of claws; regrowth of misshapen, dry, brittle, short claws * All claws/feet * idiopathic, but adverse rxn to food/drug admin possible * Large breeds predisposed * bacterial infection possible

Question 46

Histopath of lupoid onychitis

Answer 46

* interface inflammation obscurring jxn btw clawbed epithelium & adj dermis * apoptosis & vacuolation of basal cells * pigmentary incontinence