Hyperkeratosis in Dogs: Causes and Treatment
The most common cause of hyperkeratosis in dogs is a genetic disorder called keratinocyte proliferation arrest (KPCA). The condition occurs when there are abnormal changes in the genes that control cell growth. These abnormalities affect the body’s cells, including skin cells. KPCA results from mutations or deletions of two genes, TYR and MC1R. The disease affects all races of dogs, but it is more common in Golden Retrievers than other breeds.
There are several types of KPCA. Type I is characterized by a single mutation in the gene TYR. Type II involves multiple mutations in the gene TYR. A third type of KPCA is known as heterozygous KPCA, which means that one copy of the mutated gene TYR is present while another copy contains normal genes. Heterozygous KPCA is rare.
Type III KPCA results from mutations in both genes MC1R and TYR. The most severe form of this disorder occurs when both genes are affected. This type of KPCA leads to a variety of clinical signs such as skin thickening, hair loss, and liver enlargement. Other signs include joint pain, difficulty breathing, diarrhea, excessive salivation, increased appetite and weight gain. Dogs with severe cases of this condition may become lethargic, have an increased need to urinate, and may develop a fever.
The signs and symptoms of KPCA may resemble those of other conditions. Your veterinarian will perform a complete physical examination of your dog’s skin, hair, and organs to rule out other causes for the symptoms. A blood test will be done to measure the number of certain types of cells, including keratocytes. Abnormally low numbers of these cells are one indication of the disorder. A biopsy may be needed to rule out other conditions and to confirm a diagnosis of KPCA.
There is no cure for KPCA, but there are several treatment options that can help alleviate the signs and symptoms of this condition. One treatment that has proven successful with some dogs is imiquimod cream, which promotes healing by causing immune system cells to attack the affected skin. Your veterinarian can prescribe or you can buy over-the-counter 2% imiquimod cream such as Aldara. Apply a small amount to the affected areas two times daily.
Antibiotics may be prescribed if secondary skin infections are present. Your veterinarian may also recommend dietary changes to help alleviate symptoms and slow the progression of the disease, including a low-protein and low-fat diet and supplementation with essential fatty acids.
Living and Management
It is important to closely monitor the dog during treatment. If you notice any changes in behavior, such as decreased appetite or lethargy, contact your veterinarian. It is also important to closely inspect the skin of the dog for any signs of sores or infection during treatment. If these are found, contact your veterinarian immediately.
If secondary skin infections are common, your veterinarian may prescribe an Elizabethan collar to prevent your dog from scratching and irritating the skin. Be sure to clean the E-collar regularly to prevent skin infections and irritation in the area.
Continue treatment until your veterinarian recommends you discontinue use. While KPCA does not have a cure, most symptoms will improve with treatment. With time, the skin will begin to show signs of healing and regeneration. However, hair may not regrow completely and scarring may be permanent. Regular cleaning and maintenance of the skin will be needed to prevent infection and irritation in the future.
Though KPCA is incurable, most dogs affected by this disease will not require any treatment for the rest of their lives as long as signs and symptoms are treated promptly when they occur. Most dogs can lead happy and healthy lives.
Warning: Never use Imiquimod (Aldara) on humans, as it has been known to cause serious side effects including blistering of the skin.
Sources & references used in this article:
Histopathologic concept of epidermolytic hyperkeratosis by AB Ackerman – Archives of Dermatology, 1970 – jamanetwork.com
Clinical heterogeneity in epidermolytic hyperkeratosis by JJ DiGiovanna, SJ Bale – Archives of dermatology, 1994 – jamanetwork.com
Corns and calluses resulting from mechanical hyperkeratosis by DB Freeman – American family physician, 2002 – aafp.org
Mutations in the rod domains of keratins 1 and 10 in epidermolytic hyperkeratosis by JA Rothnagel, AM Dominey, LD Dempsey… – …, 1992 – science.sciencemag.org
The genetic basis of epidermolytic hyperkeratosis: a disorder of differentiation-specific epidermal keratin genes by J Cheng, AJ Syder, QC Yu, A Letal, AS Paller, E Fuchs – Cell, 1992 – cell.com
Focal acral hyperkeratosis by P M. DOWD, RRM Harman… – British Journal of …, 1983 – Wiley Online Library
Retinoic acid treatment of nipple hyperkeratosis by JM Pérez-Izquierdo, JJ Vilata, JL Sanchez… – Archives of …, 1990 – jamanetwork.com