The phenomenon of lymphocyte regression of phytohemagglutinin is a symptom of protein losing gastroenteropathy syndrome, also known as protein losing gastroenteropathy, or protein leaking gastroenteropathy or exudative gastroenteropathy. It is a syndrome caused by the loss of plasma protein, especially albumin, from the gastrointestinal mucosa due to various reasons. The main clinical manifestations are generalized swelling and hypoplasmosis. Small intestinal lymphangiectasis is often associated with immunoglobulin loss and abnormal cellular immunity, and the lymphocyte repertoire of phytohemagglutinin is diminished, making it susceptible to pulmonary infections. The exact mechanism of protein loss from the gastrointestinal tract is unknown, but the current tendency is to multi-causal theory, which is considered to be related to a variety of diseases: a. Diseases with abnormal mucosal epithelium of the gastrointestinal tract: such as hypertrophic gastritis, gastric cancer, ulcerative colitis, restricted small bowel inflammation, Crohn’s disease, intestinal cancer or any other inflammatory and ulcerative lesions, can be plasma protein leakage from the diseased mucosa into the intestinal lumen, such as exceeding the compensatory capacity of the liver. If the compensatory capacity of the liver is exceeded, hypoproteinemia will be formed. Second, diseases of the gastrointestinal tract or systemic lymphatic vessels abnormalities: thoracic duct lymphatic obstruction, constrictive pericarditis, congestive heart failure, poor intestinal lymphatic drainage, small intestine lymphatic duct dilatation, etc. The hypoproteinemia of constrictive pericarditis and congestive heart failure is mainly due to the increase of central venous pressure, which hinders the lymphatic reflux in the thoracic duct, thus causing the loss of intestinal proteins, and small intestinal lymphatic duct dilatation, which may be a congenital defect in which the rupture of the dilated lymphatic duct can cause the loss of plasma proteins and lymphocytes from the intestine. Third, diseases with increased capillary permeability: such as colon polyposis with capillary dilation, allergic gastrointestinal disease, gastrointestinal mucosal metabolic disorders, etc., all have increased capillary permeability, which leads to protein loss, typically such as adult celiac disease.