Precision medicine using whole genome sequencing in a cat identifies a novel COL5A1 variant for classical Ehlers-Danlos syndrome

BackgroundEhlers-Danlos syndromes (EDS) are a heterogeneous group of heritable connective tissue disorders occurring in both human and veterinary patients. The genetics of these disorders are poorly described in small animal patients. Hypothesis/ObjectivesDefine the clinical manifestations and genetic cause of a suspected form of EDS in a cat. AnimalsA 14-week-old male domestic medium hair cat was presented with skin hyperextensibility and fragility. The classic tragic facial expression was observed as well as chronic pruritus and mild hyperesthesia. MethodsBlood samples and a skin biopsy sample were collected from the affected cat. Clinical examinations, histology, electron microscopy and whole genome sequencing were conducted to characterize the clinical presentation and identify possible pathogenic DNA variants to support a diagnosis. Criteria defining variant pathogenicity were examined including human disease variant databases. ResultsHistology showed sparse, disorganized collagen and an increase in cutaneous mast cells. Electron microscopy identified ultrastructural defects commonly seen in collagen type V alpha 1 chain (COL5A1) variants including flower-like collagen fibrils in cross-section. Whole genome sequencing and comparison with 413 cats in the 99 Lives Cat Genome Sequencing Consortium database identified a novel splice acceptor site variant at exon 4 in COL5A1 (c.501-2A>C). Conclusions and Clinical ImportanceOur report broadens the current understanding of EDS in veterinary patients and supports the use of precision medicine techniques in clinical veterinary practice. The classification of variants for pathogenicity should be considered in companion animals.