Hereditary nasal parakeratosis in Labrador Retrievers.

Hereditary nasal dermatitis is reported in 14 Labrador Retrievers and 4 Labrador Retriever crosses. This appears to be a newly described inherited disorder for which an autosomal recessive mode of inheritance is suspected. The lesions were first noted between 6 and 12 months of age. Histopathological analysis revealed parakeratotic hyperkeratosis, often with marked multifocal accumulation of proteinaceous fluid between keratinocytes within the stratum corneum and superficial stratum spinosum. There was also a sub-basal lymphoplasmacytic infiltration within the superficial dermis. Immunohistochemistry staining for IgG (n = 4), distemper and papillomaviruses (n = 4) were negative, as were serum antinuclear antibody serology (n = 4) and fungal culture (n = 7). Electron microscopy revealed an altered cornification process: retention of nuclear chromatin, absence of lamellar bodies and marked intercellular oedema. Dogs did not respond to oral administration of zinc methionin (n = 3), cephalexin (n = 4), vitamin A alcohol (n = 1) or topical tretinoin (n = 1). Improvement of the lesions was obtained with topical vitamin E (n = 2), petroleum jelly (n = 2), and propylene glycol (n = 5).