Hypertrichosis in a horse with alimentary T-cell lymphoma and pituitary involvement.

This study focuses on the case of a 13-year-old quarter horse mare suffering from excessive hair growth (hypertrichosis), severe diarrhea, weight loss and lethargy. The horse was found to have lymphoma, a type of cancer, specifically in the gastrointestinal mucosa, mesenteric lymph nodes and pituitary gland. The study suggests that these conditions might have disrupted the hormone regulation or thermoregulatory center in the hypothalamus which led to hypertrichosis, excessive sweating, and abnormal fat distribution.

Case Details

• The aged Quarterhorse mare had a 6-month history of recurring diarrhea, progressing weight loss, and persistent lethargy.
• At the time of presentation, the mare showed signs of excessive hair growth (hypertrichosis), hyperhidrosis (abnormal excessive sweating), severe diarrhea and abnormal fat distribution.

Diagnosis and Prognosis

• The initial clinical diagnosis indicated a protein-losing enteropathy (a condition causing the loss of protein from the body due to gastrointestinal tract disorders) and pituitary pars intermedia dysfunction (a dysfunction of a specific part of the pituitary gland).
• A tissue sample taken from the mare’s rectum, however, confirmed T-cell lymphoma, a type of cancer that begins in T-cells, a type of white blood cell. This indicated that the mare was critically ill.
• Given the mare’s advanced condition and the very poor prognosis, the horse’s owner decided euthanasia was the most compassionate choice.

Necropsy Findings

• Post-mortem examination showed that the mare had an excessively enlarged pituitary gland along with hypertrichosis.
• The horse had developed a tumor in her pituitary gland, which disrupted the normal hormonal regulation in her body.
• The hyerptrichosis was thought to be triggered by the combination of abnormal growth (adenomatous hyperplasia) in a particular region of the pituitary gland (pars intermedia) and the lymphoma.
• This combination of conditions could either have disrupted the hypothalamic dopaminergic tone (a mechanism regulating the release of hormones) or interfered with the hypothalamus’ ability to regulate body temperature (thermoregulatory center).