Currently, treatments for Fabry disease are pharmacological and predominantly focus on the physical symptoms of the disease. In the general population and individuals with disabilities, increasing physical activity levels and reducing sedentary time can be an effective, non-pharmacological treatment to improve mental health and quality of life. Such interventions have not yet been developed or evaluated in people with Fabry disease.

The aim of this study is to co-design a physical activity and sedentary behaviour intervention tailored to the needs of adults with Fabry disease. The study will seek to gain the expertise of adults with Fabry disease, specialist stakeholders (physicians, cardiologists and clinical nurse specialists) and lay specialist stakeholders (family and friends of adults with Fabry disease and members of staff and volunteers at the Society for Mucopolysaccharide Diseases). A range of views and experiences of physical activity and sedentary behaviour will be explored via focus groups (with individuals with Fabry disease and lay specialist stakeholders) and semi-structured interviews (with specialist stakeholders). The information gathered from the focus groups and interviews will then be utilised to inform participatory workshops (with individuals with Fabry disease) to test intervention concepts. Data from these activities will inform the design of a future intervention.

Individuals with Fabry disease will be eligible to participate in the study if they meet the following inclusion criteria:

• Have been diagnosed with Fabry disease.
• Aged ≥ 18 years old.
• Able to independently ambulate with or without the use of a walking aid.
• Lives in the United Kingdom.
• Deemed eligible to participate following screening by a clinician (for participatory workshops).

The circumstances in which an individual may be deemed ineligible to participate in the participatory workshops based on the clinician's assessment are as follows:

• Severe neuropathic pain.
• Stage 4 heart failure or other condition resulting in breathlessness to a level they cannot participate.
• Other clinical condition which dominates the clinical picture to the extent that it dominates the symptoms and biases the results.

Exclusion criteria for all participants will be as follows:

• Incapacity to provide written informed consent.
• Unable to communicate in English to a sufficient level to permit engagement in the study.

Specialist stakeholders will be members of staff at NHS specialist centres for Fabry disease who are directly involved in the healthcare of adults with Fabry disease.

Lay specialist stakeholders will be individuals who have been involved in supporting adults with Fabry disease, such as family, friends and members of staff at the Society for Mucopolysaccharide Diseases.

Adults with Fabry disease, lay specialist stakeholders and specialist stakeholders who meet the eligibility criteria.