Background: Primary intestinal lymphangiectasia is an exceedingly rare disorder. Epidemiology is unknown. It usually presents with lower extremity swelling, diarrhea, ascites, and protein-losing enteropathy. Since the pathogenesis of edema is usually due to hypoalbuminemia; both extremities are typically involved. The edema can rarely be due to abnormal lymphatic circulation, causing lymphedema, which usually involves both extremities as well. Diagnosis is made by the constellation of clinical, biochemical, endoscopic, and histological findings. Treatment involves dietary modification, to reduce lymphatic dilation in response to dietary fat. Other pharmacologic (e.g., octreotide) and replacement measures may be indicated as well. The most serious long-term complication is intestinal lymphoma. Herein is a case of Primary intestinal lymphangiectasia presenting with unilateral lower limb swelling.Case Presentation: A 4-year-old boy presents with left foot swelling since the age of 4 months, in addition to intermittent diarrhea, and abdominal swelling. The foot swelling had been evaluated by different health care professionals in the past, and was mislabeled as either cellulitis, or congenital hemihyperplasia. Physical examination revealed mild ascites, and a non-pitting foot edema with a positive Stemmer's sign (lymphedema). Blood work revealed hypoalbuminemia (albumin 2 g/dl), and hypogammaglobulinemia. Endoscopy showed dilated lacteals throughout the duodenum. Histopathologic examination revealed massively dilated lamina propria lymphatics in the duodenal biopsies. The patient was diagnosed with primary intestinal lymphangiectasia. He was treated with high-protein and low-fat diet, and supplemental formula high in medium chain triglycerides. On follow-up, the patient's diarrhea completely resolved, and his ascites and edema improved significantly.Conclusions: The presence of unilateral lower limb edema should not preclude the diagnosis of systemic disorders, and a high index of suspicion is required in atypical presentations. A good knowledge about Primary intestinal lymphangiectasia manifestations, and physical examination skills to differentiate edema or lymphedema from tissue overgrowth can significantly aid in the diagnosis. [ABSTRACT FROM AUTHOR]