Deutsch
Hrvatski
Русский
Português
Hereditary Nasal Parakeratosis (HNPK)
| Acronym: | HNPK |
| Gene: | SUV39H2 |
| Mutation: | c.972T>G |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Hereditary nasal parakeratosis (HNPK) is an inherited skin disorder that affects the Labrador retriever dog breed. The disorder is characterized by the development of crusts and fissures on the affected dog’s nose pad. Generally, parakeratosis is a benign skin condition that causes dry and scaly skin. The disease is not contagious and some forms of it are hereditary, just like hereditary nasal parakeratosis in Labrador retrievers. The stratum corneum is the upper layer of the skin. It is composed of dead cells and as such contributes greatly to the skin’s barrier function. The cells in this layer lack nuclei and are high in keratin, an important protein for moisture retention, which keeps the skin flexible and strong. These cells are peeled off with time and replaced with new cells which are constantly being produced in the layer underneath.
In parakeratosis, the cells of the stratum corneum retain their nuclei and are not completely keratinized, which causes loss of moisture and dry skin. With time, the condition progresses and dry scales start to form, which can result in deep cracks and fissures. Symptoms develop on the nose pad of affected dogs between 6 to 12 months of age. Fissures can be a source of inflammation and bacterial infection of the nasal skin. The condition can be painful and irritating, but the affected dogs are otherwise healthy. With the progression of the disorder, changes in the nose pigmentation occur, fading from its natural dark color to a lighter pink shade.
There is no cure for hereditary nasal parakeratosis in Labrador retrievers. In order to preserve the dog’s quality of life, lifelong maintenance and treatment of the condition will be needed. The disorder is caused by a point mutation in the SUV39H2 gene. The mutation causes a delay in the differentiation of the keratinocytes in the nasal epidermis. Hereditary nasal parakeratosis is inherited in an autosomal recessive pattern. Healthy parents of an affected puppy are obligate heterozygotes and therefore carry one mutant allele. Heterozygotes have no symptoms. When mating two carriers, each cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Page N, Paradis M, Lapointe JM, Dunstan RW (2003) Hereditary nasal parakeratosis in Labrador Retrievers. Vet Dermatol 14: 103–110.
Jagannathan et al., (2013) A Mutation in the SUV39H2 Gene in Labrador Retrievers with Hereditary Nasal Parakeratosis (HNPK) Provides Insights into the Epigenetics of Keratinocyte Differentiation. PLOS Genetics, 9, e100384.