Chronic idiopathic myopathy in Icelandic horses: A case series.

This research examines the clinical presentation and muscle biopsy results of Icelandic horses with poor performance and identifies signs of a previously unspecified myopathy, leading to the suggestion that Icelandic horses showing signs of poor endurance, multi-limb lameness, or increased serum creatine kinase levels may have an underlying muscle disorder.

Objective

• The study sought to identify and characterize the unique form of myopathy, a muscle disease, which presents itself in Icelandic horses through symptoms such as poor performance and multi-limb lameness.

Methods

• The researchers examined the phenotypic traits, performed clinical tests, and made diagnoses in 17 Icelandic horses.
• Horses underwent tests to measure resting serum creatine kinase (CK) and aspartate transaminase activity, two indicators of muscle damage.
• An additional test was conducted 4-6 hours and 24 hours after exercise to measure CK.
• Biopsies of the semimembranosus muscle were taken from all horses, with the results used to split the horses into two groups: those with signs of chronic idiopathic myopathy and those with normal findings.

Results

• Twelve horses showed unspecific histological signs of muscle degeneration and regeneration consistent with myopathy.
• CK levels were significantly higher in affected horses after exercise.
• Phenomenic traits, such as rapid breathing (tachypnoea), fatigue, stumbling and reluctance to perform certain gaits (tölt or canter) were observed in horses from both groups.

Conclusions

• The limitation of this study was the small sample size and lack of a control group presenting normal performance for comparison.
• Nonetheless, the findings suggest the existence of a novel myopathy in Icelandic horses.
• It’s recommended that for Icelandic horses presenting reduced performance, multi-limb lameness and/or increased serum CK levels at rest or post-exercise, a possibility of an underlying myopathy should be considered.