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In the first published molecularly characterized feline cases, veterinarians suspected Marfan syndrome after two sibling cats were found to have unusually long limbs, lens luxation in both eyes, and aortic root dilation. Researchers then used genetic sequencing and laboratory investigations to characterize the condition. These findings describe two cats—not a validated screening rule or a standard diagnostic protocol for every cat.
What findings can raise suspicion?
The combination seen in the reported siblings was notable: long limbs, bilateral lens luxation (displacement of the eye’s lens), and an enlarged aortic root. Together, these findings prompted suspicion of Marfan syndrome; none should be treated as diagnostic on its own. The report is a case characterization, not a set of validated clinical criteria.
Lens instability has also been reported in cats without the 2026 molecular characterization. A 2011 report described primary lens instability in ten related cats across three generations. The authors considered the pedigree compatible with inheritance and FBN1 a candidate, but the reported evidence was a possible association near that gene—not confirmation that those cats shared the variant later identified in the Marfan cases. Read the 2011 report abstract on PubMed.
How was Marfan syndrome characterized in the reported cats?
The 2026 study examined two random-bred littermates with the clinical findings above. The research team combined clinical evaluation with sequencing and related laboratory work; it did not validate a routine diagnostic test or establish thresholds for diagnosing other cats.
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Genome sequencing identified an FBN1 variant
Whole-genome sequencing found a homozygous FBN1 splice-region variant, XM_023255387.2:c.2678-3C>A, located three bases upstream of exon 22. “Homozygous” means both copies of the gene carried the variant. The study reported that it was absent from a comparison cohort of more than 1,000 cats; that comparison is not a survey establishing how common the condition is. Read the study in Scientific Reports.
RNA sequencing showed an effect on splicing
Oxford Nanopore sequencing of cDNA found exon 22 skipping in 73% of transcripts in an affected cat. This is a molecular result, not a measure of disease prevalence or diagnostic accuracy. The authors described the variant as hypomorphic, or “leaky”: some normally spliced transcript remained. They suggested this residual normal transcript may help explain why the cats survived into adulthood despite carrying two altered copies.
Aortic tissue findings supported impaired fibrillin-1 function
Histopathology of the ascending aorta from an affected cat showed disrupted and fractured elastic fiber tendrils, consistent with impaired fibrillin-1 function. This tissue finding was part of the investigation; it does not mean aortic tissue sampling is an established routine diagnostic step for cats.
What should a cat owner do with these findings?
If a cat has unusual body proportions, lens displacement, or a suspected heart or aortic abnormality, ask a veterinarian to assess the signs in context. The reported combination may inform clinical suspicion, but the available study does not provide a validated checklist, clinical cutoff, or estimate of how reliably those signs identify Marfan syndrome.
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For background on the first feline cases, see Cornell University College of Veterinary Medicine’s report, which says the findings may help veterinarians recognize similar cases and could help develop genetic tests.
Is a genetic test available?
The 2026 report used sequencing to identify and investigate the variant in the two affected cats. Cornell describes genetic testing as a possible future application of the discovery; the cited sources do not establish that a validated feline Marfan test is currently available commercially or for routine clinical use. Ask your veterinarian or a veterinary genetic specialist whether any appropriate testing has since become available.
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What remains unknown?
- How common Marfan syndrome is in cats; no feline prevalence estimate is established by these sources.
- The sensitivity or specificity of any clinical finding, or a validated diagnostic threshold for cats.
- Whether the FBN1 variant from the two reported siblings explains lens instability in other cats.
- Whether a validated feline genetic test is currently available.
Cornell notes that Marfan syndrome affects about 1 in 4,000 people; that is human prevalence context and must not be applied to cats.
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