Experiences with patchy loss of pigment

[EnduroRider]

Does anyone have any experience with loss of pigment? I've come across a few with the typical pattern of vitiligo where it first appears around the eyes, muzzle and sheath amd also as bird catcher spots but never this.

He's a 9yr old, arab gelding. Born bright chestnut and greyed out very quickly. The pink patches started on his hips and then withers so I wondered if it may be pressure from rugs but it is now appearing lower down his legs too so that seems unlikely.

Only visible when he is wet, this was fresh from a wash down after canter work, and no other skin issues with him. Not sure if relevant but he is very hard to keep weight on, treated for ulcers earlier this year and now scoped clear.

Worth a blood test? If so what am I asking to test for?

ETA trying to add photos...

https://photos.app.goo.gl/t88Ksv4N55Gd6qpV6
https://photos.app.goo.gl/hJpvzHYKkM4MkMj16
https://photos.app.goo.gl/AdHi2nfrTVrLopQi7
https://photos.app.goo.gl/uvSZk3eW8zC8Db6G9
https://photos.app.goo.gl/YBNGeuSjpf1fQjed6

 

[PurBee]

I have a grey arab gelding similar age. I’ve not seen anything as dramatic as that with him but slight. The one thing i correlated to symptoms was photosensitisation - mainly through tetraploid and diploid ryegrass. He has some pink skin areas and they are prone to blistering/itchiness if on ryegrass. He can appear lethargic, rather than usual-self alert, yet also be more spooky if spooked. The symptoms can be very vague, but he also during this time was very hard to keep weight on. He wasnt keen on body being touched/brushed during ryegrass ingestion spells.

It took a while to correlate cause. But even this year he showed a sensitivity, as i introduced some ryegrass haylage after being on timothy, and mixed grass (no ryegrass) fields grazing. The introduction spurred blisters on his face within 48hrs - look like a bad bug bite, but when i clocked that the ryegrass was added, i reduced it right down to a handful, and the blister is healing. He hasnt had ryegrass for a year, so his reaction to it this time was profound and immediate.

The photosensitisation aspect of some forages can induce this in either pink-skinned horses or black skinned horses with liver issues. The liver should be processing/excreting the photoluminescing compounds in the ryegrass, and if liver is impaired theres more circulation of these compounds in the blood causing photosensitising symptoms…mild to severe depending on ingestion levels and type of ryegrass.
(Diploid and tetraploid have more of these PS compounds in them, the original perennial ryegrass less so.)

In a pink skinned horse, the PS symptoms can show, even if they have healthy liver function. Its like a white person more likely to sunburn than a black skinned person. The PS compounds make it more likely by far, the white skin will be sensitive.
Most horses are black skinned with healthy livers so can eat ryegrass all day long without symptoms.
Black or white skinned horses with dodgy liver health will both be at risk of PS plants symptoms.

Tetracycline antibiotics, other medications, ryegrass, legumes (alfalfa, peas beans soy), st johns wort, topical aloe vera, birdfoot trefoil and a few other plants …but not many…have photosensitising compounds in them.

Your gelding might not be suffering PS, but keep it in the back of your mind, and as an experiment its worth taking him off ryegrass, or reduce it to 10-15% diet intake if not eliminate it, to see if weight/skin symptoms improve.

It may be worth getting labs on his liver health. Then IF he is eating ryegrass currently - reduce/eliminate it right down, then after some time - 3 months on ryegrass free diet - get liver labs drawn again and compare results.

The rapid depigmentation from black to white skin could be genetic - but it helps to be aware of the photosensitising plants/medications owning a pink skinned horse, as that brings a host of symptoms easily attributable to something else.