- Rare disease of dogs incompletely understood.
- Presumed to have both hereditary and immune-mediated components.
- Production of autoantibodies against melanocytes results in a granulomatous panuveitis, leukoderma (depigmentation of skin) and leukotrichia (depigmentation of hair) (Hnilica, 2011).
- Akitas are predisposed but the condition has been diagnosed in a variety of breeds including Alaskan malamute, Australian shepherd, Basset hound, chow chow, dachshund, German shepherd dog, Irish setter, Old English sheepdog, Samoyed, Shetland sheepdog, Siberian husky, fox terrier and others (Campbell et al, 2013; Paterson, S., 2008).
Clinical signs
- There is an acute onset of anterior uveitis either shortly before, concurrently, or following cutaneous signs.
- Ocular signs are very striking and include photophobia, marked blepharospasm, lacrimation, conjunctival congestion, diminished or absent pupillary reflex and corneal oedema associated with anterior uveitis (Figure 2).
- Unless early treatment is instigated possible sequelae are chorioretinitis, keratitic precipitates, posterior synechiae, iris bombe, cataracts, secondary glaucoma and commonly blindness.
- Cutaneous signs consist of depigmentation of the nose, lip, eyelids, and occasionally the scrotum, vulva, anus, footpads and hard palate (Figure 1). Occasionally depigmentation is accompanied by ulceration and crusting as in the dog depicted. Generalised depigmentation has been occasionally reported also.
Differential diagnosis
- Ocular signs: conjunctivitis, foreign body, neoplasia, other immunemediated disease and toxins.
- Cutaneous signs: vitiligo, other immune-mediated disease such as cutaneous lupus erythematosus, pemphigus foliaceus, and cutaneous lymphoma.
Diagnosis
- The combination of ocular and dermatological signs is suggestive.
- History, breed, physical examination.
- Ophthalmological examination. If possible it is very helpful to refer to a specialist ophthalmologist for the initial diagnosis and treatment of the ocular signs, but also for follow-up and monitoring for possible blindnessinducing sequelae. These cases benefit from periodic ophthalmological monitoring long-term and after resolution of the cutaneous signs.
- Skin biopsy. The histopathological signs are characteristic and diagnostic. They include lichenoid interface dermatitis with large histiocytes present. There is usually pronounced pigmentary incontinence although compared to other immune-mediated disease hydropic degeneration of epidermal basal cells is rare (Yager and Wilcock, 1994).
Treatment
- Delay in seeking advice is not unusual, as was the case in the dog illustrated. Ideally early involvement of a colleague with ophthalmological expertise is optimal.
- For the uveitis – topical/ subconjunctival glucocorticoids (prednisolone, dexamethasone, triamcinolone) with 1% atropine ophthalmic solution (Paterson, 2008).
- For cutaneous lesions a combination of prednisolone (1-3mg/kg every 12 to 24 hours) and azathioprine (1.5-2.5mg/ kg every 24 to 48 hours) is often successful (Paterson, 2008).
- Other non-steroid immunosuppressive therapies include oxytetracycline and niacinamide, cyclosporine and cyclophosphamide.
Prognosis
- The prognosis for the cutaneous lesions is very good. If treated early partial or even full re-pigmentation is possible. Otherwise once any ulceration is controlled the problem is largely cosmetic.
- The prognosis for the ocular signs is fair if prompt treatment is initiated and guarded to poor if veterinary advice is delayed.
References and suggested reading
Hnilica, K. A. In: Small Animal Dermatology. A Color Atlas and Therapeutic Guide. 3rd edition; pp353-354. Elsevier, 2011.
Miller, W. H., Griffin, C. E. and Campbell, K. L. In: Muller and Kirk’s Small Animal Dermatology. 7th edition; pp465-466. Elsevier, 2013.
Paterson, S. In: Manual of Skin Diseases in the Dog and Cat. 2nd edition; pp264-265. Blackwell Publishing, 2008.
Yager, J. A. and Wilcock, B. P. In: Color Atlas and Text of Surgical Pathology of the Dog and Cat. pp103-104. Wolfe, 1994.
