Multifocal pleural cystic squamous metaplasia in a horse with chronic obstructive bronchopneumonia.

A study unravels the case of a horse suffering from severe breathing difficulty and exercise intolerance, which was later found out to have a severe case of multifocal pleural cystic squamous metaplasia and chronic obstructive bronchopneumonia.

Introduction

• The research discusses the case of a 10-year-old Knabstrupper stallion who suffered from severe dyspnea (difficulty in breathing) and exercise intolerance, leading to it being euthanized.

Detailed Study and Findings

• Upon examination after euthanasia, it was determined that the horse had severe alveolar emphysema. This condition involves damage to the air sacs (or alveoli) in the lungs, leading to shortness of breath.
• Chronic fibrosing pleuritis was found in the caudal lung of the horse. This is a condition where the membranes surrounding the lungs (pleura) become inflamed and eventually hardened or fibrotic due to chronic inflammation.
• Particularly, both the caudal lung lobes (back parts of the lungs) were found to be covered with firm, multicolored plaques – ranging from gray to yellow.
• In terms of histology, these areas of plaques consisted of circumscribed pleural fibroses (well-defined areas of hardened lung membranes) and cysts (fluid-filled sacs) formed of keratinizing squamous epithelium – a process where the epithelial cells produce keratin, a protective protein, modifying the cell’s structure and function where it should not normally be.
• Intense labeling for cytokeratins 5/6 and 10 were found through immunohistochemistry. These cytokeratins are intermediate filaments found in the intracytoplasmic cytoskeleton of epithelial tissue, indicating an abnormal presence of squamous cells, which could lead to abnormal growth or tumors.
• Moreover, it was also noted that the lungs were severely affected by chronic partially obliterative bronchiolitis and peribronchiolitis with multifocal pleural involvement. Bronchiolitis refers to inflammation of the bronchioles, the small air passages in the lungs, while peribronchiolitis is a resulting inflammation surrounding these areas. This further indicates severe damage and infection in the horse’s respiratory system.

Conclusion

• The mentioned findings of the postmortem examination indicate a severe case of multifocal pleural cystic squamous metaplasia and chronic obstructive bronchopneumonia in the horse. This research provides a deeper understanding of these conditions in equines, and highlights the necessity for further investigation into their causes and possible treatments.