Equine Dermatoses

Question 1

What are primary factors of pastern dermatitis?

Answer 1

irritants, infections, parasites and immune mediated causes

Question 2

What are perpetuating factors of pastern dermatitis?

Answer 2

secondary infections, pathological skin changes or environmental influences

Question 3

What are predisposing factors for pastern dermatitis?

Answer 3

genetic, environmental, and/or iatrogenic factors

Question 4

What is pastern leukocytoclastic vasculitis?

Answer 4

Pastern dermatitis in mature horses, unilateral or bilaterally symmetrical
Hind legs are more commonly affected
Affected non-pigmented area on distal extremities (legs, sometimes muzzle)
Gets worse in summertime (photo aggravation)
Thought to be an immune complex disease with deposition in distal limb
Well demarcated circular, painful erythematous crusts on medial and lateral pastern
Painful with edema and lameness common
Dx on histopath
Tx by avoiding light, can use steroids and pentoxy +/- abx

Question 5

Answer 5

pastern leukocytoclastic vasculitis

Question 6

What are the histopathologic findings for leukocytoclastic vasculitis?

Answer 6

intramural inflammatory cells (blood vessels)
leukocytoclasia with nuclear dust
microhaemorrhages
thickening of the vessel wall

Question 7

What are the potential etiologies of leukocytoclastic vasculitis on the distal part of the equine leg?

Answer 7

idiopathic pastern leukocytoclastic vasculitis
leukocytoclastic vasculitis due to photosensitisation or bacteria
trauma-induced vasculitis
systemic vasculitis

Question 8

What is chronic progressive lymphedema?

Answer 8

• swelling/pitting edema (lymph fluid), hyperkeratosis and fibrosis (nodules, skin folds, ulcerations) of distal limbs (hind>front) in draft horses
• starts at a relatively early age and is progressive
• frequent bacterial and chorioptic mange infections –> more lymphedema
• histopath shows Increased elastin degradation, abnormal elastin network, increase elastin antibodies in serum
  o defect in elastin leads to dilated lymph vessels and lymph retention
  o changes are more evident in very deep dermis
• supportive care, no treatment known