Pharyngeal Lymphoid Hyperplasia in Horses

Horses do not have the same type of tonsil like humans, but instead, have clusters of lymphoid tissue at the rear of their throat.

• Your horse may have difficulty swallowing depending on the severity of the pain
• A persistent cough that unsettles your horse
• Your horse may appear depressed 
• Follicular tissue inflammation
• Nasal discharge in some cases
• Lack of appetite 

Types 

• Characterised by inflammation of the upper respiratory tract in your horse
• PLH is graded by the degree of severity that the symptoms cause, classified as Grades 1, 2, 3, and 4
• Grade 1 is the least severe with minor effect on your horse
• Grade 4 the most severe causing pain and discomfort
• Grades 3 and 4 have nasal discharge 
• Prevalent in younger horses

It is not really known what triggers this condition, but your horse will grow out of it as it matures. It seems to be an immunity conditioning reflex.

• Maybe caused by dust and pollen irritants in your young horse
• Exposure to allergens that may be natural or chemical in nature 
• Bacterial infection or virus
• Usually self-healing in most minor cases

If you are concerned with your horse’s breathing or difficulty in swallowing, you should call on your veterinarian to check his condition. The veterinarian will do a physical exam of your horse, checking the throat and respiratory system. Using an endoscopy will allow a clearer picture of what is happening and what the cause of the difficulty in swallowing is. Samples from a gentle scraping of your horse’s throat can be analysed to see what is causing the problem, which can then be acted upon to treat the condition. Severe forms of PLH cause problems for your horse when exercising, and therefore, your horse may show an intolerance towards any activity. Respecting your horse and allowing time off for healing will greatly benefit the recovery time. If the condition is the grade 3 or 4 type, your horse’s breathing may sound loud or labored during exercise. 

In order to further investigate the cause for the labored breathing, your veterinarian may choose to perform additional imaging tests such as x-ray or ultrasound to rule out an obstruction or guttural pouch disorders. If the veterinarian feels neoplasia is a possibility, he may want to have a biopsy done.