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 disease should be considered on the basis of clinical manifestations, especially generalized swelling with hypoproteinemia, and can be diagnosed in combination with laboratory tests. The loss of plasma protein, especially albumin, causes a decrease in colloid osmotic pressure and a secondary increase in aldosterone, resulting in sodium and water retention, so the patient may develop generalized swelling, especially in the lower extremities. In addition, there may be pleural fluid, ascites, weight loss, anemia, etc. In children, there may be developmental disorders. Gastrointestinal symptoms may include loss of appetite, nausea, vomiting, diarrhea, and abdominal pain. Loss of calcium may induce hand and foot convulsions. Small intestinal lymphangiectasis often has loss of immunoglobulins and abnormal cellular immunity, and the lymphocyte repertoire of phytohemagglutinin is diminished, making it susceptible to lung infections.