Chapter 9 - Immune mediated

Question 1

Animals with absent or low thiopurine methyltransferase (TPMT) activity are more likely to experience which adverse effect of azathioprine?

Answer 1

Myelosuppression

Question 2

Azathioprine antagonises ______ metabolism interfering with ___ and ___ synthesis

Answer 2

purine

DNA and RNA

Question 3

How long does it take for the beneficial effects of gold compounds to be apparent?

Answer 3

Up to 16 weeks

Question 4

How long after azathioprine treatment should you wait before starting gold therapy?

Answer 4

4 weeks

Question 5

What are the reported a/e of pentoxifylline in horses?

Answer 5

Transient sweating
Behaviour changes
Conjunctivitis

Question 6

Which disease, other than PF, may show large numbers of acanthocytes on cytology?

Answer 6

Dermatophytosis (T. equinum)

Question 7

Which body sites are typically affected with PF in horses?

Answer 7

Face, legs, ventrum
Can be restricted to the face or coronary bands
Preputial and mammary areas may be targeted in some cases

Question 8

What % of horses show varying degrees of distal limb +/- ventral abdominal oedema with PF?

Answer 8

Up to 50%

Question 9

Which subepidermal blistering disease has been reported in horses?

Answer 9

Bullous pemphigoid

Question 10

Which two antigens are targeted in bullous pemphigoid in other species and which one is targeted in horses?

Answer 10

BPAg1/BP230
BPAg2/BP180/collagen XVII

BP180 is targeted in horses

Question 11

Which body sites are commonly affected in horses with bullous pemphigoid?

Answer 11

Oral cavity
MCJs
Intertriginous areas (axilla/groin)

Question 12

Name three differentials for bullous pemphigoid in horses?

Answer 12

Pemphigus vulgaris
SLE
EM
Adverse drug reaction
Vesicular stomatitis
Herpes coital exanthema
Stachybotryotoxicosis
Paraneoplastic stomatitis
Candidiasis

Question 13

What is the prognosis for bullous pemphigoid in horses?

Answer 13

Poor - early aggressive immunosuppressive treatment (e.g. steroids and Aza) indicated

Question 14

Name two cutaneous signs associated with SLE in the horse?

Answer 14

Lymphoedema of the distal limbs 
Panniculitis
MC ulcers
Patchy alopecia, scaling and leukoderma of the face, neck and trunk
Generalised exfoliative dermatitis

Question 15

Which body sites are affected in horses with CLE?

Answer 15

Face (especially lips, nostrils and periocular)
Pinnae
Neck
Shoulders
Perianal/perineal/genital

Question 16

Name two differentials for CLE in horses?

Answer 16

Photo-dermatitis
Dermatophilosis
Dermatophytosis
Demodicosis
Onchocerciasis
Vitiligo (if no overt inflammation)

Question 17

What are the histopathological findings in acute graft vs host disease in horses?

Answer 17

Varying degrees of interface dermatitis (hydropic or lichenoid or both)
Keratinocyte apoptosis
Satellitosis
May also target follicular epithelium

Question 18

What are they most common presentations of CADR in horses?

Answer 18

Contact dermatitis
Exfoliative dermatitis
EM
Urticaria

Question 19

In the horse, which infection has been associated with erythema multiforme?

Answer 19

Herpesvirus

Question 20

What are the characteristic lesions of erythema multiforme in horses?

Answer 20

Urticarial papules and plaques and/or vesicles and bullae

Question 21

How do you differentiate the urticarial lesions of EM in horses with the wheals seen in true urticaria?

Answer 21

EM lesions do not pit on digital pressure and can last for days to weeks

Question 22

In cutaneous necrotising vasculitis in horses, endothelial cells show increased expression of ICAM-1 and E-selectin. E-selectin is an adhesion molecule for which cell type?

Answer 22

Neutrophils

Question 23

Purpura haemorrhagica is the most common cutaneous vasculitis in the horse - which bacteria is it commonly associated with?

Answer 23

Streptococcus equi (strangles) or less commonly Corynebacterium pseudotuberculosis

Other bacterial and viral agents have been implicated,
as well as vaccination against S. equi.

Question 24

What % of horses with strangles develop purpura haemorrhagica?

Answer 24

1-5%

Question 25

Which type of sarcoid is a differential for alopecia areata in the horse?

Answer 25

Occult sarcoid

Question 26

In horses with alopecia areata, what is the distribution of alopecia?

Answer 26

The mane, tail, neck and face (can be present at other sites too)

Question 27

Alopecia areata in humans and dogs can be associated with dystrophy of the nail or claw, respectively, has hoof dystrophy been reported in the horse?

Answer 27

Yes

Question 28

In the study by Hoolahan et al. (2013), did horses with alopecia areata show seasonal variation in the severity of clinical signs?

Answer 28

Yes - Seventy-one per cent of horse owners surveyed in this study reported a seasonal pattern, with clinical signs typically worsening in the spring and summer. The underlying reason for this is unknown; however, variations in photoperiod and climate may play a role and it is possible that the seasonal change in severity simply coincides with the natural equine pelage cycle.

Question 29

In horses with pastern vasculitis, which legs are most commonly affected?

Answer 29

Hind legs

Question 30

Has pastern vasculitis been associated with Pseudomonas infection?

Answer 30

Yes - reported in a 13-year-old French saddle gelding with six week history of clinical signs; a pure growth of a multidrug-resistant Pseudomonas aeruginosa (MRPA) was obtained from a deep skin biopsy. Clinical remission was observed after a six week course of enrofloxacin and lesions did not recur.

Question 31

What are the most common clinical signs of purpura haemorrhagica?

Answer 31

Limb oedema and haemorrhages on mucous membranes

Question 32

Has pastern vasculitis been reported in pigmented or non-pigmented limbs?

Answer 32

Both - predominantly non-pigmented White legs - more exudative lesions Pigmented legs - more scaling

Question 33

In the study by Kaiser-Thom et al. (2021), how was the microbiota affected in cases of pastern dermatitis?

Answer 33

More severe forms of EPD (exudative and proliferative) exhibited a reduction of bacterial alpha diversity (decreased species evenness) in relation to the overgrowth of certain species (shift towards Staphylococcaceae)

Question 34

Which breeds of horse are often reported with alopecia areata?

Answer 34

Appaloosa (5/19; 26%) American saddlebred Peru paso

Question 35

What is the pathophysiology of purpura haemorrhagica?

Answer 35

Suspected that a type III hypersensitivity reaction leads to vasculitis, extravasation of albumin, and oedema. Deposition of complement around immune complexes in vessel walls leads to profound leukocytoclastic vasculitis, vascular occlusion, tissue ischemia, and infarction

Question 36

What systemic signs can be seen with purpura haemorrhagica?

Answer 36

Depression, anorexia, fever, tachycardia, tachypnoea, reluctance to move, drainage from lymph nodes, exudation of serum from the skin, colic, epistaxis and weight loss.

Question 37

Have circulating anti-keratinocyte IgG been documented in horses with PF?

Answer 37

Yes