Protein-losing enteropathy (PLE), the manifestation of a diverse set of disorders, is characterized by excessive loss of plasma proteins into the affected portions of the gastrointestinal tract, and this results in hypoalbuminemia. A 5-month-old breastfed boy presented severe PLE with hypogammaglobulinemia, hypocalcemia, and hypomagnesemia induced by an egg allergy. He developed hypocalcemic convulsions. The diagnosis of PLE was confirmed by elevated fecal alpha1-antitrypsin clearance and a positive finding on a protein-losing scintigram. His allergy to egg delivered through maternal milk was confirmed as the cause of PLE, since the mother's elimination of egg from her diet improved his condition and maternal egg challenge provoked symptoms of diarrhea, vomiting, and elevated alpha1-antitrypsin clearance. At the time of writing, he is 22 months old and has experienced no further episodes after the elimination of egg-containing food.