Researchers Review Equine Sarcoidosis Cases

While still rare, equine sarcoidosis—not to be confused with sarcoid tumors, an unrelated skin condition—can appear in even the healthiest of horses. But don’t be too quick to treat sarcoidosis-associated hair loss, scaly and flaking skin, and crusting with creams, ointments, and lotions. According to Dutch researchers, it’s better to get a reliable diagnosis before starting treatments that might be useless, or worse, painful for your horse.

“An immune-mediated disease like sarcoidosis is not going to get better with washes and topical treatments,” said Marianne Sloet van Oldruitenborgh-Oosterbaan, DVM, PhD, Dipl. ECEIM, Specialist KNMvD Equine Internal Medicine, from the Department of Equine Sciences at Utrecht University. “Some horses’ skin actually becomes painful from all the various local treatments. It’s important to get an early diagnosis to know what you’re up against.”

Although sarcoidosis is visible on the skin, with its typical hair loss and crusting, flaking, scaling, and sometimes nodules, it’s sometimes a full-body disease that can attack the lungs and other organs—even bone marrow, Sloet said.

To better understand how sarcoidosis can affect the horse and to help owners and veterinarians determine treatment options, Sloet and colleague Guy C.M. Grinwis, DVM, PhD, Specialist KNMvD in veterinary pathology, also of Utrecht University, looked at 22 equine sarcoidosis cases at their university clinic between 2002 and 2011.

They found that equine sarcoidosis can be divided into three rather distinct categories: local, generalized, and partially generalized. Local sarcoidosis appears to only affect a very specific area of skin, usually on the legs. Generalized sarcoidosis might show skin lesions on various parts of the horse’s body and will also cause internal problems.

While you can’t really see these “interior” problems on a living horse, Sloet said, you can see some or all of their effects: low-grade fever, reduced performance or unwillingness to work, slightly faster breathing even at rest, difficulty breathing, coughing, and sometimes weight loss, especially if the horse has had the disease for more than a few months. Partially generalized sarcoidosis does not appear to run this deep, but it will still show skin lesions in more than one area of the body, Sloet said.

The treated horses in this retrospective study received either intravenous or intramuscular corticosteroid therapy for a generalized treatment, Sloet said. Researchers have previously proved corticosteroid therapy to be effective against sarcoidosis, and oral prednisolone might be helpful in later stages, she added.

In their review, none of the horses with generalized or partially generalized sarcoidosis recovered from the disease, and they were all euthanized. In the horses with general sarcoidosis, Sloet and Grinwis identified lesions on the animals’ internal organs during necropsy, she said.

The good news, said Sloet, was that most of the horses (68.2%) had the local form of the disease. What’s more, these cases never became generalized, not even up to 10 years later.

The horses with local disease had a much better chance of survival than the other cases, said Sloet. While some healed with treatment, others eventually healed without any treatment at all. About half of the horses continued to have local sarcoidosis, which was not life-threatening but sometimes painful and usually unsightly, she said.

“In those cases, some of the owners chose to have their horses euthanized, and their insurance companies agreed with the choice,” Sloet said.

“Recognition of the different forms of sarcoidosis based on history, clinical signs, and histopathology can assist owners in making an informed choice between treatment and euthanasia and can prevent unnecessary topical treatment strategies,” she concluded.

The study, "Equine sarcoidosis: clinical signs, diagnosis, treatment and outcome of 22 cases," appeared in Veterinary Dermatology in February 2013.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.