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Vitamin A-Responsive Dermatosis
Vitamin A-responsive dermatosis is not a systemic vitamin A deficiency but a local deficiency in the skin, a disorder of skin utilization, or a pharmacological effect of high doses on the skin. Cocker Spaniels have the highest incidence although a similar condition has been reported in Labrador Retriever, Miniature Schnauzer, and Chinese Shar-pei.
All animals have a physiological requirement for active vitamin A (retinol). However, most mammals, including the dog but with the exception of the cat, have the ability to convert vitamin A precursors to active vitamin A. The most common forms of preformed vitamin A in foods are derivatives of retinol, such as retinyl palmitate and retinyl acetate. The largest quantities of these compounds are found in fish liver oils and animal livers.
The 2008 Association of American Feed Control Officials
(AAFCO) Nutrient Profiles for dog foods recommends that dog foods containing an energy density of 3.5 kcal/kg should include a minimum of 5000 IU/kg for growth, reproduction, and adult maintenance. This value is equivalent to 1500 RE/kg diet.
Anything that interferes with the absorption with vitamin A or enhances its excretion can result in a relative deficiency. Since oversupplementation can result in toxicity, the levels of vitamin A administered should be carefully monitored.3
Signs
Clinical signs are usually present by 2 to 3 years of age and are very similar to those seen in primary idiopathic seborrhea. Clinical signs include recurrent scaling, a dry hair coat with easy epilation, and prominent comedones. Plaques are most prominent on the chest and abdomen. Ear infections are common and itchiness is variable.
Diagnosis and Treatment
The early age of onset of skin scaling with plaques in a Cocker Spaniel is usually a reason to suspect a clinical diagnosis.
A preliminary diagnosis is made from skin biopsy findings. However, even with the classic clinical findings, a definitive diagnosis can be confirmed only by the response to supplementation with vitamin A alcohol.
Vitamin A alcohol is recommended for the life of the patient. Improvement is seen within 4 to 6 weeks. Complete remission is obtained by 10 weeks of treatment and is well-tolerated in dogs with no significant side effects. Medicated shampoos containing benzoyl peroxide (oxyDex, Sulf OxyDex, Pyoben) have excellent follicular flushing activity. Twice to three times weekly usage helps remove keratinous debris from follicles and hastens recovery.
References
- Scott, Miller, Griffin. Small Animal Dermatology, 5th ed., Philadelphia, WB Saunders
2. Nesbitt & Ackerman. Canine & Feline Dermatology, 1st ed., New Jersey, Veterinary Learning Systems
- Lowell Ackerman. Nutritional Supplements in Canine Dermatoses
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