I take immunosuppresive & other drugs for rheumatoid arthritis. Is there severe risk from hand foot and mouth disease if a child in my family has it?

If you are unlucky. Persons on immuno-suppressive meds have a suppressed immune system! They should avoid sick people, if at all possible. Wearing a medical face mask, along with good hand-washing, can help avoid catching viruses. The current coxsackie a6 strain, in the news, is causing worse hand-foot-mouth symptoms than the typical strain. Bad symptoms include high fevers, vomiting, diarrhea, brain problems, etc...