A 16-year old girl was admitted for chronic diarrhea, generalized edema, severe pain of lower extremities, and general weakness. She could not walk because of burning pain of knee and ankle. 99mTc-MDP bone scan demonstrated increased periarticular uptake in both lower extremity with focal increased activity in proximal portion of both tibias.. Abnormal abdominal activity in ascending, transverse, and descending colon is also seen. Bone densitometry showed severe osteoporosis in lower extremity. 99mTc-HSA scan showed abnormal radioactivity in small bowel, and descending colon indicating protein losing enteropathy. Endoscopic biopsy of terminal ileum showed a few dilated lymphatics in the submucosa. After steroid and supplemental therapy, the symptoms and signs of both protein losing enteropathy and RSDS much improved simultaneously. Reflex sympathetic dystrophy syndrome is a complex of symptoms characterized by severe pain, swelling, autonomic vasomotor dysfunction, and impaired mobility of affected extremities. The important causes are trauma, fracture, and inflammation. We assumed that the reflex sympathetic dystrophy syndrome of this girl was due to protein losing enteropathy. And as far as we know there has not been reported case that protein losing enteropathy assumed as a cause of reflex sympathetic dystrophy syndrome.