Canine zinc-responsive dermatosis
Zinc is essential for more than 300 enzymes, structural proteins and hormones in the mammalian body. It is needed for diverse physiological processes and metabolic functions including many aspects of the immune system, including iodine (thyroid) metabolism.
Lack of zinc is associated with atrophy of the thymus, a gland that has a role in the maturation of lymphocytes, and it seems the function of T lymphocytes is especially vulnerable to deficiency of this mineral.
With zinc deficiency, there is a reduction in delayed type hypersensitivity, and other immune responses mediated by T cells. Reduction in the production of antibodies and in the function of natural killer cells has also been reported in experimentally induced zinc deficiency in animals.In addition, zinc is needed for cell replication and is thus essential for the regeneration of the intestinal mucosa, the healing of wounds and the turnover of epithelial cells necessary to maintain healthy skin, hair and nails.
It is also important in maintaining normal sexual function.
The combination of these essential functions explains why zinc plays such an important part in the protection against infections.
The first reported case of zinc-related disease in the dog was reported in the journal, Growth, in an Alaskan Malamute with chondrodysplasia. It was found that these Malamutes absorbed only 25 percent of zinc in the small intestine compared to normal controls, and furthermore, the reduction in absorption was related to the inability to release protein-bound zinc to the non-protein-bound status at the gut level. This transfer occurs in normal dogs. This zinc-related disease (in this case, no skin problems were reported) in this breed has been later reported to cause skin lesions even with animals on a well-balanced commercial dog food.
True zinc deficiency is quite rare; it only has been reported in the Bull Terrier with lethal acrodermatitis.
This condition demonstrates a dysfunctional zinc metabolism and probable malabsorption in the small intestines. Stunted growth, diarrhea, numerous cutaneous or internal infections, and crusted and fissured paw pads are seen. The internal infection usually manifests as pneumonia and is directly related to diminished cellular immunity. Puppies usually die or are euthanized.
The affected dogs do not respond to oral or intravenous zinc supplementation.
There are basically three other syndromes of zinc-related dermatoses in the dog.
Most cases have been well-documented and seen in the past, but less so recently. This may be due to better breeding and improvements in the quality of canine commercial diets.
The first type occurs in Alaskan breeds including the Siberian Husky and Alaskan Malamute.
It has also been reported in Doberman Pinschers and Great Danes.
The affected dogs were all on a well-balanced commercial dog food that was sufficiently supplemented with zinc. It appears the skin disease is a result of several causes, primarily related to a genetic defect in intestinal absorption. This has been well documented in the Alaskan Malamute breed. The onset in the appearance of skin lesions has been also linked to estrus, severe stress, or severe diarrhea.
Also, the planum and the paw pad epithelium may also display similar changes as seen on the haired skin.