Tetragametic chimerism (including Freemartinism)
Also known as: Chimerism · Chimaerism · Freemartinism · XX/XY leukocyte chimerism
Overview
What it is
This is a rare developmental accident where a dog develops from two different fertilized eggs that fused together in the womb, resulting in a single animal with two distinct sets of DNA. In cases involving male and female twins, known as freemartinism, hormone sharing can cause abnormal development of the reproductive system. Because this is an embryological mishap rather than an inherited genetic disease, it cannot be detected using standard commercial canine DNA panels.
How it presents
Many affected dogs show no symptoms at all, but females may fail to go into heat, prove infertile, or have unusual external genitalia. These signs are typically noticed when the dog reaches sexual maturity, usually between 6 and 18 months of age.
Treatment
The condition itself does not require treatment, but if anatomical issues or infections arise, a one-time surgery or spaying may be necessary. These procedures are highly effective and typically cost between 150 and 1500 EUR.
How it's tested
Affected breeds
Treatment cost
Estimated range of typical treatment cost. Actual cost depends on severity, clinic and region.
Frequently asked
What is Tetragametic chimerism (including Freemartinism)?
This is a rare developmental accident where a dog develops from two different fertilized eggs that fused together in the womb, resulting in a single animal with two distinct sets of DNA. In cases involving male and female twins, known as freemartinism, hormone sharing can cause abnormal development of the reproductive system. Because this is an embryological mishap rather than an inherited genetic disease, it cannot be detected using standard commercial canine DNA panels.
How is Tetragametic chimerism (including Freemartinism) tested?
Various clinical and genetic tests are used depending on the breed and presentation.
Which breeds are most affected?
This condition isn't tied to a specific breed in our database.