Ichthyosis (DSP-related)

 

Gene: DSP

Transmission: Autosomal dominant

For an autosomal dominant genetic disease, an animal must have at least one copy of the mutation in question to be at risk of developing the disease.  Animals with two copies of the mutation generally have more severe symptoms and an earlier onset of the disease than animals with just one copy of the mutation.  One or both of the parents of an animal with the mutation has one or two copies of the mutation, except in the case of de novo mutations.  Animals that have one or two copies of the mutation can pass the mutation on to future generations.

Mutation: Deletion, DSP gene: c.1821_1823 del., p.(Asp608 del.), Chr.35.

Medical system: Dermal, dental

Breed: Miniature Poodle

Age of onset of symptoms: From an early age.

Ichthyosis refers to a family of skin diseases that disrupt normal skin structure and function and give a scaly appearance to the skin.  “Ichthy-” refers to fish, as in fish scales.  Ichthyosis is a very common condition in the canine population with both genetic and environmental contributing factors.  Hereditary ichthyosis can present as non-syndromic, with lesions only within the skin, or as syndromic, where skin lesions are accompanied by lesions in other systems.

A ten-month-old Miniature Poodle presented with skin that was rough, dry, inelastic, irregular in thickness and had scales (squames).  In addition, the dog had hyperkeratosis of paw pads, dry eye, reduced hair with regional alopecia and dental abnormalities.  A diagnosis of syndromic ichthyosis was made.  Molecular studies identified a heterozygous mutation in the DSP gene as a likely candidate for the phenotype.  The DSP gene codes for a protein component of desmosomes, which are intercellular junctions involved in cell adhesion and resistance to mechanical force.  Mutations in the DSP gene are a known cause of ichthyosis in humans.  The identified canine mutation was not seen in 270 additional poodles genotyped.  Because the mutation was heterozygous in the single dog displaying symptoms and the fact that both parents were clinically normal, it was considered a spontaneous (de novo) mutation.  It can be considered of academic interest but not of concern to breeders and veterinarians.

Hereditary ichthyosis in the dog can be caused by numerous genetic defects, and tend to be gene and breed specific:

KRT10 gene: Epidermolytic hyperkeratosis (ichthyosis)

SLC27A4 gene: Ichthyosis (Great Dane type)

ABHD5 gene: Ichthyosis (Golden Retriever, type 2)

NIPAL4 gene: Ichthyosis (American Bulldog type)

PNLA1 gene: Ichthyosis (Golden Retriever type)

TMG1 gene: Ichthyosis (Jack Russell Terrier type)

 

References:

OMIA link: [2243-9615]

Kiener S, Lehner G, Jagannathan V, et al. (2024) Heterozygous DSP in-frame deletion in a poodle with syndromic ichthyosis involving additional hair and tooth abnormalities. Anim Genet 55:725-732.  [pm/39136317]

 

With contributions by: Anne-Sophie Goyer and Florence Gaudreault, Class of 2030, Faculty of Veterinary Medicine, University of Montreal.  (Translation: DWS).