Evaluation of the Filum Terminale in Hereditary Equine Regional Dermal Asthenia.
Authors: McElroy Abigail, Klinge Petra M, Sledge Dodd, Donahue John E, Glabman Raisa A, Rashmir Ann
Journal: Veterinary pathology
Summary
# Editorial Summary: Filum Terminale Pathology in Hereditary Equine Regional Dermal Asthenia HERDA horses exhibit striking structural and ultrastructural abnormalities in the filum terminale (the terminal filament of the spinal cord) that mirror those seen in human Ehlers-Danlos syndrome patients with tethered cord syndrome—a potentially debilitating condition where abnormal cord attachment causes progressive neurological damage. This study compared filum terminale samples from four HERDA-affected and five control horses using histopathology, immunohistochemistry, and electron microscopy, alongside comparative analysis of human tissue samples. Both HERDA horses and EDS patients demonstrated hypervascularity and moderate to severe disorganisation of collagen fibrils—including abnormal orientation, architecture, swelling, and fragmentation—which were absent in unaffected controls. Because tethered cord syndrome in human EDS patients remains poorly understood, HERDA provides a valuable naturally-occurring large animal model for investigating the pathophysiology of stretch-induced spinal cord injury and potentially developing interventions. Equine practitioners should consider that the systemic collagen defects characterising HERDA may have neurological consequences beyond skin fragility, warranting investigation of subtle gait abnormalities or behavioural changes in affected animals.
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Practical Takeaways
- •HERDA horses with spinal cord involvement may develop progressive neurological signs related to cord stretching; farriers and handlers should be alert to gait changes, weakness, or sensory loss, especially in hindquarters
- •This research validates the horse as a natural disease model for human EDS research, potentially advancing understanding of connective tissue disorders that affect both species
- •Collagen structural abnormalities in HERDA affect not just skin but also spinal cord support structures, suggesting systemic connective tissue fragility beyond dermal manifestations
Key Findings
- •Equine filum terminale in HERDA horses showed moderate to severe abnormalities in collagen fibril orientation and architecture similar to human EDS-TCS patients
- •Hypervascularity was observed in both HERDA horses (n=4) and human EDS-TCS patients but not in control horses (n=5) or human controls
- •Equine and human filum terminale are anatomically similar, containing fibrous tissue, ependyma, neuropil, and nerve twigs
- •HERDA horses represent a viable animal model for understanding the pathophysiology of tethered cord syndrome in human Ehlers-Danlos syndromes