Pathology of Natural Cases of Equine Endocrinopathic Laminitis Associated With Hyperinsulinemia.
Authors: Karikoski N P, McGowan C M, Singer E R, Asplin K E, Tulamo R-M, Patterson-Kane J C
Journal: Veterinary pathology
Summary
Hyperinsulinaemia has emerged as the leading endocrine trigger of laminitis, yet the microscopic tissue damage characteristic of this condition remained poorly defined in naturally occurring cases due to reliance on experimental models with varying protocols and incomplete clinical documentation. Karikoski and colleagues examined lamellar tissue from 14 hyperinsulinaemic horses and ponies (insulin >20 mIU/l) with clinical laminitis against 25 control animals matched for age and breed, mapping precisely where pathological changes occurred and their relationship to disease duration. The researchers identified a distinctive pattern of abaxial (outer) lamellar pathology featuring apoptotic cell death, tissue fusion, hyperplasia, and aberrant keratinised material with nucleated debris, which created irregular margins between the inner horn and lamellae; surprisingly, lesion severity bore no correlation with how long horses had shown clinical signs, suggesting substantial tissue damage accumulates before lameness becomes apparent. Separation initiated from the abaxial region with notably minimal inflammation—a key distinction from inflammatory laminitis models—whilst axial lamellar tapering predominated on the inner aspect, supporting the hypothesis that repeated subclinical episodes precede overt clinical presentation. For practitioners, these findings underscore that hyperinsulinaemic horses likely experience progressive lamellar compromise long before owners notice gait changes, emphasising the critical importance of insulin screening in at-risk individuals and aggressive metabolic management to prevent cumulative tissue damage.
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Practical Takeaways
- •Hyperinsulinemic laminitis develops through subclinical episodes before obvious clinical signs appear—early insulin testing and management of at-risk horses (obese, Cushings, metabolic syndrome) is critical for prevention.
- •The abaxial location of lesions in endocrinopathic laminitis differs from inflammatory laminitis, suggesting different underlying mechanisms that may require distinct therapeutic approaches.
- •Lesion severity at necropsy does not predict clinical duration, so mild clinical signs do not guarantee minor pathological changes; consistent long-term management of insulin regulation remains essential even after apparent recovery.
Key Findings
- •Lamellar lesions in hyperinsulinemic laminitis were predominantly abaxial, featuring apoptotic cell death, lamellar fusion, hyperplasia, and keratin replacement with nucleated debris.
- •Lesion severity and type showed no correlation with reported clinical duration, suggesting subclinical laminitis episodes precede clinical presentation.
- •Acute separation originated from the abaxial region with minimal inflammation, and extensive basement membrane failure was absent unlike in inflammatory laminitis models.
- •Axial epidermal lamellar tapering was the most frequent morphological observation in chronic cases.