Laryngospasm, dysphagia, and emaciation associated with hyperkalemic periodic paralysis in a horse.

This research discusses a case of an 18-month-old Quarter Horse suffering from weight loss and difficulty swallowing (dysphagia) which was later attributed to hyperkalemic periodic paralysis (HPP). HPP was treated successfully, implying the disease should be considered for similar symptoms, regardless of age or serum potassium levels, in horses, particularly those associated with Quarter Horse breeding.

Introduction to the Case

• The presented case describes an 18-month-old Quarter Horse gelding (a castrated male horse) displaying symptoms of weight loss and dysphagia, both of which had persisted for one month.
• The horse was lethargic, dehydrated, had excessive salivation (ptyalism), and was suspected of suffering from aspiration pneumonia – a type of lung infection due to inhaling food, stomach acid, or saliva into the lungs.
• Severe breathing difficulty (dyspnea) and bluish discoloration of the skin (cyanosis) were observed especially after light physical activity.

Clinical Examination

• Through an endoscopy, a medical procedure involving the insertion of a long, flexible tube down the throat, the medical experts discovered laryngospasm and pharyngospasm – intense involuntary contractions of the larynx and the pharynx, respectively.
• After considering both the clinical signs and endoscopic findings, they suspected the horse to have hyperkalemic periodic paralysis (HPP), a genetic disorder that disrupts muscle cell function causing episodes of muscle weakness or paralysis.

Treatment: Acetazolamide and Its Effects

• Based on their suspicions, the horse was treated with acetazolamide, a diuretic often used to alleviate symptoms in individuals diagnosed with HPP.
• The treatment led to a significant improvement in the horse’s condition within a 48 hour period, further supporting the diagnosis of HPP.

Diagnosis Confirmation

• After observing the response to treatment, the horse was confirmed to be homozygous for HPP, meaning it inherited two copies of the abnormal gene, one each from both its parents.
• The dysphagia, weight loss, and aspiration pneumonia in this case were identified as clinical manifestations and outcomes of HPP.

Implications for Horses of Quarter Horse Breeding

• The study suggests that, in the investigated populations, regardless of the age and serum potassium concentration, HPP should be assessed as a potential diagnosis for horses specifically of Quarter Horse breeding if they exhibit symptoms like pharyngeal and laryngeal irregularities or dysphagia.