MPSIIIB in Schipperke Dogs: Causes, Symptoms, and Testing

Mucopolysaccharidosis type IIIB, also called MPSIIIB or Sanfilippo syndrome B, is a hereditary lysosomal storage disease found specifically in the Schipperke dog breed in the UK. This genetic disorder leads to the deficiency of a vital enzyme called alpha-N-acetylglucosaminidase (NAGLU), responsible for breaking down complex molecules called glycosaminoglycans, especially heparan sulphate.

Without a functioning NAGLU enzyme, heparan sulphate accumulates abnormally inside tiny sacs in the cells called lysosomes. This buildup disrupts cellular function and causes progressive degeneration, chiefly affecting the nervous system.

Understanding MPSIIIB: Genetics and Progression

MPSIIIB is inherited as an autosomal recessive condition, meaning a dog must inherit two copies of the faulty gene—one from each parent—to be affected. Dogs with only one mutated gene are carriers; they remain healthy but can pass the mutation on to their offspring.

Early biochemical changes can be detected even in puppies as young as one month, but clinical symptoms typically appear between two and four years of age. These symptoms progress over time, affecting brain and neurological functions.

Common Symptoms in Affected Schipperkes

• Progressive ataxia (loss of coordination and balance)
• Tremors affecting the whole body and head
• Cognitive decline and mental dullness
• Abnormal gait, including exaggerated limb movements and trunk swaying
• Difficulty walking and climbing obstacles, often worsening over time
• Possible behavioural changes such as lethargy or aggression

Due to the progressive nature of MPSIIIB, the quality of life deteriorates substantially, and humane euthanasia is usually considered between four and six years of age.

Diagnosis and Preventing MPSIIIB Spread

Since the condition is caused by a specific gene mutation, a simple DNA test can determine whether a Schipperke is clear, a carrier, or affected. Testing is carried out by sending samples to specialised laboratories approved by The Kennel Club. This testing is vital for responsible breeders aiming to reduce MPSIIIB incidences within the breed.

Responsible breeding decisions are essential to ensure dogs with MPSIIIB genes are not bred together, preventing affected litters and gradually reducing the mutation's presence in the population.

Genetic Inheritance Patterns Explained

Understanding mating combinations helps predict litter outcomes:

• Two clear dogs produce clear litters.
• Two carriers have a 25% chance of affected puppies, 50% carriers, and 25% clear.
• A carrier and a clear dog produce 50% carriers and 50% clear offspring.
• An affected dog bred with a carrier results in 50% affected and 50% carriers.
• An affected dog bred with a clear dog produces 100% carrier puppies.
• Two affected dogs produce 100% affected puppies.

Why Testing Matters for Schipperke Owners and Breeders

Testing empowers owners and breeders with crucial knowledge to maintain the health and wellbeing of this cherished breed, preventing the spread of a debilitating, incurable neurological disease. It also supports ethical breeding practices that prioritise animal welfare over profit.

If you own a Schipperke or are considering finding a Schipperke puppy, ask your breeder about MPSIIIB testing results, and consider testing your own dog if status is unknown.

Further Research and Hope

MPSIIIB in Schipperkes not only affects the breed profoundly but also provides an important model for researching similar human diseases, opening doors for potential therapies in both veterinary and human medicine.

While no cure currently exists, keeping informed and practising responsible breeding offers the best hope of protecting future generations of Schipperkes from this tragic condition.