First documented cases of Marfan syndrome found in two cat siblings

Scientists have identified the first documented cases of Marfan syndrome in domestic cats after two feline brothers, Gary and Shaggy, were found to have the rare genetic disorder.

The siblings showed signs of the condition from a young age, including unusually long limbs. As they grew older, veterinary examinations also revealed abnormalities affecting their eyes and enlargement of the aorta, the main artery carrying blood away from the heart. These findings led researchers to investigate whether the cats had Marfan syndrome, a connective tissue disorder best known in humans.

The condition affects around one in 4,000 people and is associated with changes to connective tissues throughout the body, including those in the eyes, bones, ligaments, skin and blood vessels. Until the cases of Gary and Shaggy, it had not been documented in cats.

Researchers from Cornell University’s College of Veterinary Medicine and Baker Institute for Animal Health worked with specialists from Ghent University in Belgium, the University of Pennsylvania and the Schwarzman Animal Medical Center in New York City. The team combined detailed veterinary examinations with genetic sequencing to determine the cause of the cats’ symptoms.

The investigation identified changes in the FBN1 gene, which provides instructions for producing fibrillin-1, a protein that is important for healthy connective tissue. Both Gary and Shaggy carried two altered copies of the gene, with one inherited from each parent.

The finding was particularly unusual because, in humans, a single altered copy of FBN1 can cause Marfan syndrome, while inheriting two altered copies is extremely rare. Researchers discovered that the specific variant carried by the cats did not completely stop the gene from functioning. Instead, it disrupted how the gene's instructions were processed while still allowing some normal function.

That partial function may help explain why Gary and Shaggy survived into adulthood despite carrying two altered copies of the gene. The study found that the genetic variant caused exon 22 to be skipped in a large proportion of the gene's transcripts, while a smaller amount of normally processed genetic material was still produced.

The researchers described the discovery as an important step towards improving veterinary diagnosis of the condition. Dr Jacquelyn Evans, the study’s senior author and an assistant professor at Cornell’s Baker Institute for Animal Health, said the findings could help veterinarians recognise similar cases in the future and potentially contribute to the development of genetic tests.

The findings were published in Scientific Reports on September 19 in a study titled A homozygous hypomorphic FBN1 splice region variant in domestic cats with Marfan syndrome. Researchers said the cases also demonstrate how studying naturally occurring genetic disorders in animals can provide comparative insights into conditions that affect humans.