Chapter 9 - Immune mediated Flashcards
Animals with absent or low thiopurine methyltransferase (TPMT) activity are more likely to experience which adverse effect of azathioprine?
Myelosuppression
Azathioprine antagonises ______ metabolism interfering with ___ and ___ synthesis
purine
DNA and RNA
How long does it take for the beneficial effects of gold compounds to be apparent?
Up to 16 weeks
How long after azathioprine treatment should you wait before starting gold therapy?
4 weeks
What are the reported a/e of pentoxifylline in horses?
Transient sweating
Behaviour changes
Conjunctivitis
Which disease, other than PF, may show large numbers of acanthocytes on cytology?
Dermatophytosis (T. equinum)
Which body sites are typically affected with PF in horses?
Face, legs, ventrum
Can be restricted to the face or coronary bands
Preputial and mammary areas may be targeted in some cases
What % of horses show varying degrees of distal limb +/- ventral abdominal oedema with PF?
Up to 50%
Which subepidermal blistering disease has been reported in horses?
Bullous pemphigoid
Which two antigens are targeted in bullous pemphigoid in other species and which one is targeted in horses?
BPAg1/BP230
BPAg2/BP180/collagen XVII
BP180 is targeted in horses
Which body sites are commonly affected in horses with bullous pemphigoid?
Oral cavity
MCJs
Intertriginous areas (axilla/groin)
Name three differentials for bullous pemphigoid in horses?
Pemphigus vulgaris SLE EM Adverse drug reaction Vesicular stomatitis Herpes coital exanthema Stachybotryotoxicosis Paraneoplastic stomatitis Candidiasis
What is the prognosis for bullous pemphigoid in horses?
Poor - early aggressive immunosuppressive treatment (e.g. steroids and Aza) indicated
Name two cutaneous signs associated with SLE in the horse?
Lymphoedema of the distal limbs Panniculitis MC ulcers Patchy alopecia, scaling and leukoderma of the face, neck and trunk Generalised exfoliative dermatitis
Which body sites are affected in horses with CLE?
Face (especially lips, nostrils and periocular) Pinnae Neck Shoulders Perianal/perineal/genital
Name two differentials for CLE in horses?
Photo-dermatitis Dermatophilosis Dermatophytosis Demodicosis Onchocerciasis Vitiligo (if no overt inflammation)
What are the histopathological findings in acute graft vs host disease in horses?
Varying degrees of interface dermatitis (hydropic or lichenoid or both)
Keratinocyte apoptosis
Satellitosis
May also target follicular epithelium
What are they most common presentations of CADR in horses?
Contact dermatitis
Exfoliative dermatitis
EM
Urticaria
In the horse, which infection has been associated with erythema multiforme?
Herpesvirus
What are the characteristic lesions of erythema multiforme in horses?
Urticarial papules and plaques and/or vesicles and bullae
How do you differentiate the urticarial lesions of EM in horses with the wheals seen in true urticaria?
EM lesions do not pit on digital pressure and can last for days to weeks
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?
Neutrophils
Purpura haemorrhagica is the most common cutaneous vasculitis in the horse - which bacteria is it commonly associated with?
Streptococcus equi (strangles) or less commonly Corynebacterium pseudotuberculosis
Other bacterial and viral agents have been implicated,
as well as vaccination against S. equi.
What % of horses with strangles develop purpura haemorrhagica?
1-5%
Which type of sarcoid is a differential for alopecia areata in the horse?
Occult sarcoid
In horses with alopecia areata, what is the distribution of alopecia?
The mane, tail, neck and face (can be present at other sites too)
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?
Yes
In the study by Hoolahan et al. (2013), did horses with alopecia areata show seasonal variation in the severity of clinical signs?
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.
In horses with pastern vasculitis, which legs are most commonly affected?
Hind legs
Has pastern vasculitis been associated with Pseudomonas infection?
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.
What are the most common clinical signs of purpura haemorrhagica?
Limb oedema and haemorrhages on mucous membranes
Has pastern vasculitis been reported in pigmented or non-pigmented limbs?
Both - predominantly non-pigmented
White legs - more exudative lesions
Pigmented legs - more scaling
In the study by Kaiser-Thom et al. (2021), how was the microbiota affected in cases of pastern dermatitis?
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)
Which breeds of horse are often reported with alopecia areata?
Appaloosa (5/19; 26%)
American saddlebred
Peru paso
What is the pathophysiology of purpura haemorrhagica?
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
What systemic signs can be seen with purpura haemorrhagica?
Depression, anorexia, fever, tachycardia, tachypnoea, reluctance to move, drainage from lymph nodes, exudation of serum from the skin, colic, epistaxis and weight loss.
Have circulating anti-keratinocyte IgG been documented in horses with PF?
Yes
