Zinc-responsive dermatosis

A rare scaly skin disease, zinc-responsive dermatosis is the result of zinc deficiency, zinc malabsorption, or inappropriate zinc use. Zinc is essential for more than 300 enzymes, structural proteins and hormones in mammals. It is required for multiple physiological processes and metabolic functions, including many aspects of the immune system, including iodine (thyroid) metabolism. Zinc deficiency is associated with atrophy of the thymus, a gland that plays a role in lymphocyte maturation, and it appears that T lymphocyte function is particularly susceptible to this mineral deficiency. During zinc deficiency, delayed-type hypersensitivity reactions are reduced and other immune responses mediated by T cells are reduced. Reductions in antibody production and natural killer cell function have also been reported in experimentally induced zinc deficiency in animals.

In addition, zinc is required for cell replication and therefore is essential for the regeneration of the intestinal mucosa, wound healing and epithelial cell renewal necessary to maintain healthy skin, hair and nails. Maintaining normal sexual function is also important. Zinc-responsive dermatosis can occur for several reasons and can cause symptoms such as redness, scaling, crusting, and hair loss.

There are many clinical manifestations in dogs:

Syndrome I--occurs almost exclusively in northern breeds of dogs (eg: Siberian Husky and Alaskan Malamute) and is characterized by poor zinc absorption or genetic damage in metabolism (genetic problems).
Syndrome II - Rapidly growing large breed puppies consuming a high-phytate diet, a zinc-deficient diet, or a diet supplemented with ingredients that may inhibit zinc absorption.

In syndromes I and II, redness occurs at mucocutaneous junctions and pressure points (due to blocked capillaries in the lower layers of the skin). In addition, scaling, scabbing, alopecia, pyoderma, and lichenification may occur, primarily on the dog's head. In severe cases, anorexia, lethargy, growth retardation, purulent paronychia, pyoderma of the distal limbs, and peripheral lymphadenopathy are evident. Cutaneous lesions include widespread erythematous, crusted papules, often pruritic, with hyperkeratosis, erythema, and swelling of the soles of the feet. Visual abnormalities such as corneal vacuoles

How to treat reactive skin disease

1. Diagnosis is based on histological examination of the affected skin, demonstrating reduced zinc levels in the blood (normal = 0.8-2.0 ppm) and response to treatment. Demonstration of low zinc concentrations in serum and hair is of definite value only for the diagnosis of zinc-responsive dermatoses in dogs and must be correlated with response to treatment.

2. Zinc can be given as a daily oral supplement of zinc gluconate (10 mg/kg/day orally), and in severe cases, intravenous zinc sulfate (10 mg/kg) may be required. Treatment should be continued for 1 month to determine response to treatment, and if the initial dose is ineffective, the daily dose should be increased by 50%

3. Additional treatment including antibacterial treatment, if needed, periodicallyBathing with a cuticle shampoo (such as sulfur and salicylic acid) may be beneficial (Bayer malaseb is recommended)

There are early reports of some dogs (especially puppies) developing scale and scabs within 2 to 4 weeks of being fed commercial general purpose dog food! The food did not meet National Research Council requirements and contained suboptimal zinc levels. Lesions can be well defined at the mucocutaneous junction, pressure points, and distal extremities, and are associated with varying degrees of alopecia. The puppy also had fever, depression, peripheral lymphadenopathy, and pitting edema.