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Friday, May 3, 2013

Arytenoid Chondritis in a Horse

A 12 year old quarter horse mare presented for a 2-3 month history of coughing and "wheezing". The mare had developed the symptoms some what suddenly and was responsive to systemic corticosteroids. As such, it was initially thought that the mare was developing signs of heaves or COPD (chronic obstructive pulmonary disease). Heaves is relatively common in the southeastern United States and is a chronic progressive condition that involves an allergic condition that affects the lungs and causes fibrosis and scarring.     At presentation, the client was interested in finding out for sure what was causing the coughing and wheezing. Re-breathing exam was essentially normal with no wheezing detected or coughing. The mare was currently being treated with corticosteroids and had been for the past 48 hours. The initial plan was to scope the mare and perform a bronchoalveolar lavage (BAL) to confirm the diagnosis of heaves. However, when the endoscope was passed to the point of the larynx, we discovered what was the true problem!

Figure 1
In Figure 1 and 2, the larynx of the horse in question appears grossly abnormal. In Figure 1, the horse is in between breaths and there is thin slit between the arytenoids which consists of her airway. In Figure 2, the mare is taking a deep breath and the full extend of her airway is probably the diameter of a sharpie pen! There is large linear ulcer that crosses the left arytenoid cartilage and the significant thickening of both left and right arytenoid cartilages suggest chronic inflammation. In Figure 3, a "normal" endoscopy demonstrates what the full extent of the airway should be during inspiration and what normal arytenoid cartilage should look like!

Figure 2

Figure 3

Arytenoid chondritis is a relatively common cause of coughing and nasal discharge in older horses. This mare was a bit on the young side to have developed this condition. The causative agent is not clear but it is believed to be a combination of chronic irritation that is made worse by bacterial infection. In my experience, I have diagnosed this problem in horses that were exposed to a chemical irritant in agriculture setting such as dairy farms and produce farms; however, I have not been able to determine what chemical is causing the problem. Unfortunately  once the condition becomes chronic and the arytenoids are permanently disfigured, the only viable option is to perform a permanent tracheotomy. Surprisingly  horses do very well with permanent tracheotomies as long as they do not go swimming!! Clinical signs will improve with systemic corticosteroids and throat spray however these treatments will NOT reverse the damage done!!  This case, once again, demonstrate the importance of an endoscopic exam EARLY in the disease process.

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