This condition which presents as chronic crusting and fissuring of the nasal planum was identified in Labrador retrievers (and their crosses) nearly 15 years ago but it is still often not widely recognised in general practice. The onset of the condition is generally between six months and two years of age with dogs of either sex and any coat colours potentially affected. The hyperkeratosis is generally restricted to the nasal planum although it may extend onto the nasal dorsum in more chronic cases.
There are several conditions capable of causing nasal hyperkeratosis including viral diseases (distemper), autoimmune diseases (pemphigus foliaceus or erythematosus and discoid lupus erythematosus), inherited diseases (ichthyosis), nutritional diseases (zinc responsive dermatosis) and metabolic diseases (hepatic cutaneous syndrome) as well as infectious conditions such as dermatophytosis or Malassezia dermatitis. Differentiation between these conditions and hereditary nasal parakeratosis is important for appropriate treatment options and requires biopsies.
Histologically nasal parakeratosis is fairly distinctive and is characterised by marked parakeratotic hyperkeratosis generally with marked multifocal accumulation of proteinaceous fluid (serum lakes) between keratinocytes in the stratum corneum and superficial stratum spinosum. There is sometimes a patchy lymphoplasmacytic interstitial to interface component.
The condition was suspected to be an autosomal recessive lesion and this has been confirmed subsequently by genetic testing as a monogenic autosomal recessive mutation in the SUV 39 H2 gene. This genetic condition is not thought to result from hyperproliferation of keratinocytes but delayed terminal differentiation. An inexpensive commercially available genetic test is now available (through ASAP /Orivet) for this condition and to identify carrier animals.
Currently this condition has only been identified in Labrador retrievers but recently a possible similar condition in an unrelated species has been seen at ASAP and is under investigation.
Treatment for this condition is symptomatic only and topical application of propylene glycol in water or white petrolatum is generally effective but continued applications are required to manage the condition.
References:
1) Hereditary nasal parakeratosis in Labrador Retrievers.
Vet Dermatol. 2003 Apr;14(2):103-10.Pagé N, Paradis M, Lapointe JM, Dunstan RW.
2) Hereditary nasal parakeratosis in Labrador retrievers: 11 new cases and a retrospective study on the presence of accumulations of serum ('serum lakes') in the epidermis of parakeratotic dermatoses and inflamed nasal plana of dogs
Vet Dermatol. 2003 Aug;14(4):197-203. Peters J, Scott DW, Erb HN, Miller WH.
3) A Mutation in the SUV39H2 Gene in Labrador Retrievers with Hereditary Nasal Parakeratosis (HNPK) Provides Insights into the Epigenetics of Keratinocyte Differentiation
PLoS Genet. 2013 Oct; 9(10): e1003848.Published online 2013 Oct 3.
Vidhya Jagannathan, Jeanette Bannoehr et al
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