Genetic basis of Hereditary Nasal Parakeratosis - in Labrador Retrievers it is an autosomal recessive inherited disorder caused by a point mutation in the SUV39H2 gene, which encodes a histone methyltransferase involved in epigenetic regulation of keratinocyte differentiation. Dogs must inherit two copies of the mutated gene (one from each parent) to be affected; carriers with one copy show no clinical signs but can pass the mutation to offspring. This defect delays keratinocyte differentiation in the nasal epidermis, leading to the disorder.
Pathophysiology - HNPK causes abnormal keratinization of the nasal planum skin, wherein the upper skin layer cells (stratum corneum) retain their nuclei and fail to completely keratinize, resulting in dry, scaly, and crusty skin. This leads to loss of moisture, formation of rough scales, fissures, and deep cracks on the nose and surrounding areas. These fissures cause irritation, inflammation, and may become infected. Over time, pigment may fade from the nose, changing from dark to lighter shades.
Complications - Affected dogs develop dry, rough crusts and fissures on the nasal tip and adjacent skin areas, which can cause severe discomfort and pain in extreme cases. The lesions often predispose the skin to bacterial infections. Over time, the nose may lose pigment. Though not life-threatening, the chronic condition requires ongoing management to reduce discomfort and prevent secondary infections.
Why This Matters to Breeders and Vets - Breeders must be aware that HNPK is inherited in an autosomal recessive pattern, meaning two carriers can produce affected puppies. Genetic testing for the SUV39H2 mutation is available and important in breeding decisions to reduce disease incidence. Veterinarians need to diagnose HNPK early and provide supportive topical treatments (such as moisturizers or specific ointments) to alleviate symptoms and prevent infections. Long-term management is necessary to preserve quality of life. Awareness of the disorder allows both vets and breeders to counsel owners appropriately on prognosis, care, and breeding risks.
Summary - Hereditary Nasal Parakeratosis (HNPK) in Labrador Retrievers is an autosomal recessive genetic disorder caused by a mutation in the SUV39H2 gene leading to defective keratinocyte differentiation in the nasal skin. Clinical signs develop between 6-12 months of age, presenting as dry, crusted, and fissured nasal skin prone to infection and depigmentation. While not life-threatening, it causes discomfort requiring lifelong topical management. Genetic testing helps breeders prevent the disease by avoiding carrier matings, and veterinarians support affected dogs with symptomatic treatment and infection control.