Lacing is white lace looking markings that appear along the spine. It's also called marbling, cobwebbing catbacked, or giraffe markings. The veterinary term is reticulated leukotrichia. It usually starts along the spine and goes outwards on the back. Sometimes there's just a little bit and sometimes it covers the entire back. It appears over time as the pony ages.

The marking are likely from an autoimmune response or a fungal scarring. There have been some cases in other breeds where lacing appears to run in families which gives the appearance of it being genetic. The reaction that causes the markings would be the genetic part, not the markings themselves. Only one occurrence has been found so far in Chincoteague Ponies.

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Lacing on the middle back of a black tobiano. Developed in her early teens and the only known occurrence in her family.

Misty's Storm Chaser (Cezanne x Misty's RainDrop)
Pedigree