Diet-related zinc-responsive skin disease in dogs: a dying dermatosis?

In the United Kingdom, most cases of zinc-responsive skin disease in dogs result from feeding soya and, or, cereal-based diets, possibly, in some animals, in association with an apparent inherent defect of zinc absorption. Most such diets are not deficient in zinc but contain excessive quantities of other substances which reduce its availability for absorption. Important clinical signs include a dull, harsh coat with or without achromotrichia, erythema, seborrhoea sicca, bilaterally symmetrical, circular to linear, white/yellow crusts affecting the head, limbs, scrotum and perineum, ceruminous otitis and peripheral lymphomegaly. The diagnosis is suggested by the history, physical signs, laboratory tests and the examination of skin biopsies and is confirmed by an unequivocal response to oral zinc supplementation (10 mg/kg zinc sulphate once daily with food) while keeping the original diet unchanged. Non-specific laboratory tests (serum alkaline phosphatase, cholesterol and thyroxine concentrations before and after thyroid stimulating hormone administration) reported by others as being abnormal in some cases of zinc-responsive dermatosis have been unhelpful but a plasma zinc concentration below the mean of the reference range supports the diagnosis. The classical histological change of zinc-responsive dermatoses, parakeratosis, has been seen in only 64 per cent of cases biopsied. Long term management necessitates a change in diet to canned meat and biscuit. Long term therapy is not required. Many manufacturers of diets predisposing to the condition are now adding additional zinc to their diets resulting in a dramatic reduction in the numbers of new cases of the condition being seen.