Mucopolysaccharidosis type IIIB (MPSIIIB) in the Schipperke dog breed

Mucopolysaccharidosis type IIIB or MPSIIIB for short is a hereditary health condition that has been identified in the gene pool of some dogs of the Schipperke breed, and is also sometimes known as Sanfillippo syndrome.

The condition is a type of lysosomal storage disease, which affects the body’s enzymes leading to a range of systemic problems that ultimately prove fatal in affected dogs.

The body’s lysosomes are tiny sacs or pockets within the dog’s cells, which are filled with a specific type of enzyme that disassembles other molecules to keep the dog healthy and well. If the necessary enzymes are not present due to a health condition such as Mucopolysaccharidosis type IIIB, the disassembly process cannot be performed properly, causing the improperly degraded molecules to accumulate in the lysosomes, which in turn leads to cell death and disease.

The specific compound that accumulates in cases of Mucopolysaccharidosis type IIIB is heparan sulphate, and the missing enzyme is known as NAGLU.

In dogs affected by the condition, the disease is progressive and lead to clinical symptoms that affect the brain and neurological messages, such as poor balance, problems with walking normally and general mobility, and issues with climbing obstacles such as steps. It can also lead to uncontrolled tremors that progressively worsen too.

The initial symptoms of the condition usually present in dogs between the ages of two and four, and generally, affected dogs are euthanized within a year or two of diagnosis, due to their progressively worsening quality of life. The condition cannot be cured or treated, and is not contagious-the only means of transmission of Mucopolysaccharidosis type IIIB is by means of inheritance, and the condition is presently only found in the UK within the Schipperke dog breed.

In order to reduce incidences of the condition in the Schipperke breed and limit the spread of the condition across the wider gene pool of the breed, The Kennel Club oversees a testing and monitoring scheme for the condition, which allows would-be Schipperke breeders to find out the status of their own dog, and that of any potential mating match.

In this article, we will look at Mucopolysaccharidosis type IIIB in the Schipperke breed in more detail, including how the heredity of the condition works and how to get your own dog tested. Read on to learn more.

More about Mucopolysaccharidosis type IIIB

Mucopolysaccharidosis type IIIB is a lysosomal storage disease, and these can come in various different forms and types, each of which needs to be tested for separately. They occur due to a gene mutation-with a different gene affected in each case, hence the need for individual testing-and affect the functions of the lysosomes.

Lysosomes are small sacs within the cells that contain digestive enzymes, to break down large molecules and pass the component parts of them onto other parts of the cells to be processed and recycled. If the necessary enzymes are not present due to a mutation-causing gene, the large molecules continue to accumulate to dangerous levels within the cells, ultimately leading to premature cell death.

What sort of dogs can be affected by the condition?

In the UK, Mucopolysaccharidosis type IIIB is found in the Schipperke dog breed, which means that any dog of the breed whose status is unknown may potentially be either a carrier of or affected by the condition.

Additionally, cross-breed dogs with one Schipperke parent may potentially inherit one of the two copies of the gene mutation that can cause the condition from the Schipperke side of their ancestry and so, become a potential carrier for the condition themselves, but will not develop the affected form of the condition unless their other parent also carries the gene mutation and passes it on too.

How does the heredity of the condition work?

Mucopolysaccharidosis type IIIB is classed as an autosomal recessive hereditary condition, which means that the combination of genes any given dog inherits from both sides of their parentage is what dictates their ultimate status for the condition.

Dogs are designated as either clear, carrier or affected, with carriers being healthy themselves, but able to pass on the gene mutation for the condition to their offspring.

Different combinations of parent status lead to different results for their litter, outlined as follows:

• Two clear dogs will have a clear litter.
• Two affected dogs will have an affected litter.
• Two carriers will have a mixture of 50% carriers, 25% affected and 25% clear.
• A clear dog and a carrier will have 50% clear and 50% carriers.
• A clear dog and an affected dog will have a litter of carriers.
• A carrier and an affected dog will have 50% carriers and 50% affected.

How to get your dog tested for their status

In order to find out your own dog’s status and so, whether or not they are healthy and will produce healthy puppies, a simple DNA test is all that is required.

You will just need to ask your vet to take a DNA sample from your dog, and send it off to one of The Kennel Club’s approved laboratories, who will then return the results of your dog’s status.