Primary intestinal lymphangiectasia (PIL) or Waldmann's disease is a rare protein-losing gastroenteropathy of unknown etiology. Less than 200 cases have been reported globally. Patients may be asymptomatic or present edema, lymphedema, diarrhea, ascites and other manifestations. We report two pediatric cases with PIL with extremely different outcome in a 3-year follow-up period. The first patient presented with persistent diarrhea, hypoalbuminemia and failure to thrive, while the second patient presented with an abrupt eyelid edema. Hypoproteinemia was the common laboratory finding for the two patients and upper gastrointestinal endoscopy established the diagnosis. The first patient relapsed five times during the follow-up period after the diagnosis had been made and required intravenous albumin administration and micronutrient supplementation. The second patient revealed normal gastrointestinal endoscopy 4 months after the diagnosis had been established; he followed an unrestricted diet and remained asymptomatic throughout the follow-up period. PIL can be either severe, affecting the entire small bowel, leading to lifetime disease, or sometimes affects part of the small bowel, leading to transient disorder.