Suffering From Multiple Oral Ulcers In Mouth, Cheek And Tongue, Very Painful. Step To Cure This?

Sir, My mother is suffering from multiple oral ulcers for past 20 years. the ulcers are big and it occurs all over the mouth, like cheeks, tongue , retromolar region. the ulcers are very painful and even a white layer is peeling off. It is not candidiasis , after the removal of the white layer it apears erythematous. They said it is due to some secretion defect in oral cavity. No similar ulcers in other parts of the body. We took all blood and othe rnecessary investigations. Even the endoscopy result is negative.They prescribed Prednisolone 20 mg BD and ENDOXAON 50 OD. Please tell me what is the step to cure her ulcers, She is 47 years old now. She is taking this medicines for past 12 years. What is the disgnosis of her condition, y they prescribed Cyclophosphamide? Please help her