Pedigree analysis in dogs has shown that the disorder is a recessive trait, which means that an affected animal inherits a copy of the responsible gene from each parent. "I wouldn't be surprised if the disease in horses follows the same genetic pattern as what we see in dogs," says Henson. "It is so similar in all other respects."
There is no treatment for color-dilute follicular dysplasia, so Charlie's hair would not be growing back. "I honestly thought the owner might choose to put the horse down when we explained the problem to her," says Henson. "But she said it didn't bother her and she took him home. We made regular follow-up calls for about three years to see how he was getting on."
A pasture pet before his diagnosis, Charlie continued to live on full turnout. In cold weather, he obviously needed heavy blankets, and his owner was vigilant about making sure he didn't get chilled. In the summer, the gelding wore an artificial tail extension, so insects did not seem to bother Charlie any more than they did his pasturemates. He was, however, more prone to sunburn. On sunny days, he was protected with a light sheet.
"Grooming this fellow was easy," says Henson. "But he would get a bit greasy. Oils that normally coat the hairs just pooled on the skin. They handled that by bathing him when it got bad."
Nearly four years after his diagnosis Charlie was sold, and Henson has since lost track of her unusual patient. "He's a lovely horse with a great personality," she says. "I wouldn't be surprised if he's keeping someone very happy just being himself."
As a gelding, Charlie will not be passing color-dilute follicular dysplasia to any offspring, but Henson says she suspects that other affected horses are out there.
"I haven't come across one myself or even read about one in the scientific literature, but I'm pretty certain there are more," she says. "They are probably gorgeously colored horses being treated for chronic ringworm by very frustrated owners." Henson says it's easy to identify color-dilute follicular dysplasia in such cases. "A skin biopsy is not difficult or expensive, and the condition is easy to diagnose by a pathologist familiar with the condition in dogs. It's extremely rare, but something that can be ruled out early on."
This article originally appeared in the June 2004 issue of EQUUS magazine.
