How to build your first UX design portfolio?

I have already completed the UX Basics course and I've reached a bit of a roadblock in regard to creating a UX design portfolio. I am transitioning from a career in cognitive rehabilitation therapy. I have been working with people who have cognitive and/or communication impairments, which means I'm an expert in how the brain works (memory, processing, sequencing, design making, attention, cognitive load, verbal language, non-verbal language, etc.). I modify environments (and the staff/families in them) in order to create environments in which my clients can operate with the greatest independence (and joy!) possible. My skills are very transferable as I've been essentially doing UX in physical environments (for individuals).

I am especially interested in the information architecture, usability, and research side of UX design. How could I best represent my work on a portfolio, since I have no visuals and can't divulge great detail due to HIPAA? In healthcare is acceptable to create composite case studies to discuss assessment/research, best practices, and client/user modifications. Is that acceptable within UX design also?

Thank you very much for your help!