My father suffered from this for years until we found a doctor who actually knew how to treat it instead of pretending to know. It's an auto-immune disorder that causes blisters to form all over the body. Until he was treated correctly, my father was in a lot of pain from the blisters.
The dermatologist he originally saw had him on 5mg of prednisone daily. When we finally convinced him to see another dermatologist, he upped the dosage to 40 mg daily for a couple of weeks. The results were almost immediate. After that initial blast, he was eventually weaned down to a dosage that would maintain the results.
The second doctor told us that until steroids were developed in the '50s, bp was usually fatal as blisters would eventually form in the throat and block the airway. My father was experiencing blisters in his throat when his treatment regimen was changed. I shudder to think that his death would have been hastened by this disease if he hadn't switched doctors.
Edited to add: Because it's fairly rare, you'll run into a lot of medical professionals who don't know what it is. When my dad was briefly in a nursing home, the doctor there discontinued the prednisone without consent because he didn't see a need for it even though it was in my father's chart. Be prepared to explain whenever your mother faces a hospitalization or a new doctor.