Among primary immunodeficiencies, common variable immunodeficiency (CVID) is defined by an impaired production of immunoglobulins characterized by low levels of plasma immunoglobulins and an altered antibody response. The case reported here was initially interpreted as a CVID. A 20 year old male suffered from diarrhea, weight loss, and malnutrition. Accurate diagnostic assessment uncovered a protein-losing enteropathy. Conventional oil contrast lymphangiography accurately documented the underlying problem and established the appropriate therapeutic approach. The operation consisted of multiple antigravitational ligatures of dilated and incompetent chylous vessels and chylous vessel-mesenteric vein microanastomoses. Serum albumin and leukocyte counts normalized by 1 week after operation and remained stable with time. There were no more episodes of diarrhea, and the patient regained weight. Accurate diagnostic assessment and particularly lymphangiography may be necessary to properly define difficult cases of immunodeficiency due to intestinal protein loss and to plan a corrective therapeutic functional approach.