This research study will investigate whether people with vascular Ehlers-Danlos syndrome (vEDS), a rare inherited condition, have problems with the way their body stores and uses fat (adipose tissue). vEDS is caused by changes in a gene called COL3A1, which makes a protein important for the structure of many tissues. While vEDS is best known for making blood vessels fragile, there is some early evidence that it may also affect fat tissue and increase the risk of problems such as insulin resistance (where the body does not respond properly to insulin) and diabetes.

Fat tissue is important for keeping the body healthy. It stores extra energy, but it also sends signals to other organs. If fat tissue cannot expand or work properly, fat can build up in the liver or muscles instead, leading to high blood sugar, high cholesterol, and greater risk of diabetes and heart disease.

In this study, we will invite 12-17 adults with genetically confirmed vEDS to take part, along with a group of age-, sex-, and weight-matched controls without vEDS. Participants will attend a research visit at Addenbrooke's Hospital, Cambridge. They will have measurements of body fat distribution (using a DEXA scan), a liver scan, blood tests, and a standard oral glucose tolerance test (drinking a sugary drink with blood samples before and after). Some participants may also choose to provide a small fat biopsy under local anaesthetic to allow more detailed analysis of tissue structure.

The main aim is to see whether people with vEDS show changes in fat distribution and insulin sensitivity compared to those without vEDS.

Inclusion Criteria:

• Age over 18 years
• Confirmed pathogenic or likely pathogenic COL3A1 mutation with vascular Ehlers-Danlos syndrome
• Capacity to provide informed consent

Exclusion Criteria for those with vEDS:

• Current corticosteroid use
• Pregnancy or lactation
• Acute illness at the time of assessment

Exclusion criteria for control participants

• Current corticosteroid use
• Pregnancy or lactation
• Acute illness at time of assessment
• Confirmed COL3A1 mutation
• Gastrointestinal or bariatric surgery (except cholecystectomy and appendectomy)

Participants with vascular Ehlers-Danlos syndrome and BMI, age, ethnicity and gender matched controls