X-linked myotubular myopathy / XLMTM (MTM1-related) - Labrador Retriever

What does this test examine?

This genetic test detects the MTM1 variant c.465C>A that causes X-linked myotubular myopathy in Labrador Retrievers. The condition is also known as XLMTM, myotubular myopathy, myotubular myopathy 1 or MTM1-related muscle disease.

Affected puppies develop a severe muscle disease with marked weakness, difficulty moving, reduced muscle tone, swallowing or breathing problems and rapid deterioration. Because the disorder is X-linked, males carrying the variant are mainly affected; females with one copy are important carriers in breeding programmes.

Practical value of this test

• Identifies carriers in Labrador Retriever and related lines before matings are planned.
• Helps prevent affected male puppies from being produced in risk combinations.
• Supports breeding selection where muscle weakness, early losses or XLMTM risk are relevant.
• Provides clear information for family screening, selection of breeding animals and communication with puppy buyers.

Inheritance and interpretation

XLMTM is inherited as an X-linked recessive disorder. A male with the altered variant on his only X chromosome develops the disorder. A female with one copy is a carrier and can pass the variant on; two altered copies in a female would represent an affected genotype.