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- First Confirmed Case of Degenerative Myelopathy in Boston–Frenchie Mix
First Confirmed Case of Degenerative Myelopathy in Boston–Frenchie Mix
JSAP 2025
Obi Veterinary Education
August 29, 2025
A. M. K. Chan, J. R. Coates, G. C. Johnson, H. N. Snyman, D. W. Silversides
Background
Degenerative myelopathy (DM) is a progressive neurodegenerative disease in dogs linked to mutations in the SOD1 gene, particularly the SOD1:c.118G>A variant. While genetic risk has been documented in Boston terriers and French bulldogs, histopathological confirmation of DM has not previously been reported in these breeds. This case study presents the first confirmed diagnosis of DM in a Boston terrier–French bulldog mix, aiming to highlight clinical progression and diagnostic pathways.
Methods
An 8-year-old neutered male Boston terrier–French bulldog mix with progressive pelvic limb ataxia was evaluated. Initial diagnostics included full neurologic examination, spinal MRI (T3-sacrum), cerebrospinal fluid (CSF) analysis, and genetic testing. Over 37 months, serial MRIs and neurological exams were performed to monitor disease progression. Following euthanasia, post-mortem MRI and histopathologic analysis of the spinal cord were conducted, including immunohistochemistry with anti-SOD1 antibodies.
Results
Initial MRI and CSF analysis were unremarkable, yet the dog was homozygous for the SOD1:c.118G>A mutation. Progressive signs included worsening paraparesis, tetraparesis, incontinence, and muscle atrophy. Post-mortem MRI revealed severe spinal cord and epaxial muscle atrophy. Histopathology showed widespread axonal loss, astrogliosis, and neuronal degeneration consistent with end-stage DM. Immunohistochemistry confirmed SOD1-positive cytoplasmic aggregates in spinal neurons, establishing a definitive diagnosis.
Limitations
This single-case report limits generalizability. Advanced MRI techniques (e.g., diffusion tensor imaging) were not employed, and quantitative spinal cord metrics were not used. The causal relationship between the mutation and disease in this dog, while strongly suggestive, cannot exclude contribution from other genetic or environmental modifiers.
Conclusions
This report documents the first histologically confirmed case of DM in a Boston terrier–French bulldog mix and provides valuable insights into disease manifestation in small breeds. Genetic testing for SOD1 mutations should be considered in these breeds when clinical signs are compatible. Serial MRI may aid in tracking disease progression. The findings support routine screening of breeding dogs and emphasize the diagnostic value of combining genetic and imaging modalities.
Sagittal T2-weighted magnetic resonance imaging (MRI) of the thoracolumbar spine on initial presentation (A) and post mortem (B). Transverse T2-weighted MRI images of the spinal cord at the level of the T12–T13 intervertebral disc on initial presentation (C) and on post mortem (D). Note the reduction in the cross-sectional area of the spinal cord and widening of the subarachnoid space in both sagittal and transverse planes in the post mortem study. The triangular appearance was consistent with spinal cord atrophy. There was also marked epaxial muscle atrophy, thoracolumbar kyphosis and static diffuse intervertebral disc desiccation.
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