Rosai-Dorfman disease is a rare disorder where there is overproduction and accumulation of a specific type of white blood cell (histiocyte) in the lymph nodes of the body causing lymphadenopahy, most often those of the neck. whrein the cause is unknown. and the signs and symptoms vary from one person to another. in many cases there is spontaneous remission (without treatment) of this disease ranging within months to years. others may undergo surgery for removal of the histiocytic lesion. and in some serious cases, a steroid given, or alpha interferon, others are anticancer drug. and since the health of your mother is deteriorating then what we can do is symptomatic and supportive treatment. like for example if your mother had fever then will give the antipyretic or if she had other complaints, then will give the specific drug for that complaint.