Todayโs path rounds are on ๐๐จ๐ง๐ ๐๐ง๐ข๐ญ๐๐ฅ ๐ก๐ฒ๐ฉ๐จ๐ญ๐ก๐ฒ๐ซ๐จ๐ข๐๐ข๐ฌ๐ฆ ๐๐ง๐ ๐๐ฒ๐ฌ๐ฆ๐๐ญ๐ฎ๐ซ๐ข๐ญ๐ฒ ๐ฌ๐ฒ๐ง๐๐ซ๐จ๐ฆ๐ (CHD)! This was a request 
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
CHD is a syndrome of foals primarily characterized by enlarged thyroid glands and deformities of the limbs. This syndrome was first described in Western Canada by one of my current professors. Small world!
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
Foals get this condition!
๐๐ก๐๐ญ ๐๐๐ฎ๐ฌ๐๐ฌ ๐ข๐ญ?
The exact cause is still unknown, however there have been many proposed causes. The cause that has the most support currently is low dietary ๐ข๐จ๐๐ข๐ง๐ in the motherโs diet, which leads to inadequate iodine for the growing foal.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
Inadequate iodine is one of the major causes of ๐ ๐จ๐ข๐ญ๐ซ๐ (thyroid gland enlargement) in any species, and that is one of the main findings in these foals. Other common findings associated with CHD are ๐๐ฅ๐๐ฑ๐ฎ๐ซ๐๐ฅ ๐ฅ๐ข๐ฆ๐ ๐๐๐๐จ๐ซ๐ฆ๐ข๐ญ๐ข๐๐ฌ (limbs that are permanently flexed), ๐ข๐ง๐๐จ๐ฆ๐ฉ๐ฅ๐๐ญ๐ ๐ฃ๐จ๐ข๐ง๐ญ ๐จ๐ฌ๐ฌ๐ข๐๐ข๐๐๐ญ๐ข๐จ๐ง (soft bones in the joints) and ๐ฆ๐๐ง๐๐ข๐๐ฎ๐ฅ๐๐ซ ๐ฉ๐ซ๐จ๐ ๐ง๐๐ญ๐ก๐ข๐ฌ๐ฆ (severe underbite). These foals also often have signs of ๐๐ฒ๐ฌ๐ฆ๐๐ญ๐ฎ๐ซ๐ข๐ญ๐ฒ (excessively long gestation preventing proper growth) such as a silky hair coat and floppy ears.
Because of the skeletal changes in these foals, they often are not able to stand up, and if they can, their underbite prevents them from suckling normally.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
The veterinarian can make the diagnosis by assessing the foal for the skeletal changes listed, and the presence of signs of dysmaturity and an enlarged thyroid gland.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
Unfortunately there is no treatment for these foals. Due to their soft joint bones, they have an extremely poor prognosis because if they do stand, their body weight will collapse the soft joint bones and prevent them from ever growing properly. For this reason, these foals are often euthanized.
๐๐ก๐จ๐ญ๐จ๐ฌ
1) A foal with flexural abnormalities. In these cases, the foal is completely unable to straighten its legs.
2) An X-ray showing incomplete ossification of the bones of the knee joint. Normally each of those bones should have a square, angular appearance, and a strongly white periphery.
3) Enlargement of the thyroid gland at necropsy.
4) Another consequence of flexural abnormalities is ๐ซ๐ฎ๐ฉ๐ญ๐ฎ๐ซ๐ ๐จ๐ ๐ญ๐ก๐ ๐ญ๐๐ง๐๐จ๐ง๐ฌ. In this poor foal, their ๐๐ข๐ ๐ข๐ญ๐๐ฅ ๐๐ฑ๐ญ๐๐ง๐ฌ๐จ๐ซ ๐ญ๐๐ง๐๐จ๐ง (extends the leg joints) ruptured because of the severity of their leg flexion.
5) An example of mandibular prognathism in a CHD foal.
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Koikkalainen K, Knuuttla A, Karikoski N, Syrjรค P, Hewetson M. Congenital hypothyroidism and dysmaturity syndrome in foals: first cases reported in Europe. Equine Veterinary Education 2014;26(4):181-189.
Photos 1-5 ยฉ Koikkalainen et al.
