Incontinentia pigmenti


Good news!   

Your horse is clear of incontinentia pigmenti and does not have the gene mutation.   

Your horse cannot pass on the incontinentia pigmenti gene mutation. There are no breeding or performance implications. 

What is incontinentia pigmenti?

Incontinentia pigmenti is only seen in female horses since male fetuses with the mutation die before birth. Females that inherit the mutation are born brindle, with dark pigmentation down the Blaschko lines. Affected horses suffer from hair loss, unpleasant skin lesions and teeth, hoof, and eye deformities.

Genomic Details

Incontinentia pigmenti is caused by a mutation in the IKBKG gene. This gene is responsible for activating a protein which is important for the immune system, fetal development, and inflammation. Horses with the disease gene version of the IKBKG gene do not activate this protein. This results in incontinentia pigmenti.

Immune-mediated myositis is a dominant genetic disease. This means only one gene mutation from one parent is needed for the disease to occur.

The mutation that causes incontinentia pigmenti is a switch in one of the four base pairs that make up a DNA molecule. Cytosine (C) is replaced by Thymine (T) changing the IKBKG gene. Therefore, a horse’s genetic result for incontinentia pigmenti is one of three possibilities:

  • C/C: Normal. Does not have the disease. Does not have the mutation.

  • C/T: Affected. Has one disease mutation from one parent. This is enough to cause the disease. It might be passed to their foal.

  • T/T: Affected. Has two disease gene mutations, one from each parent. One mutation will be passed to their foal.