Hello, Peter,
My husband is the Myeloma patient, now been on the treatment for 5 months. Your post struck me because that is almost exactly what happened to him after three weeks of trouble-free regime. The rash spread very quickly all over his body, and I had no end of problems getting an appointment for someone to see him. Eventually he was told to stop all the medication, and come in for a review. It seems that the culprit was Thalidomide, so that might be the same for you. The good news is that there are different medications that do the same job as Thalidomide. Best wishes for your continuing treatment.
Lili