Pathological conditions in the intestines that are characterized by the gastrointestinal loss of serum proteins, including serum albumin; immunoglobulins; and at times lymphocytes. Severe condition can result in HYPOGAMMAGLOBULINEMIA or lymphopenia. protein-losing enteropathies are associated with a number of diseases including INTESTINAL lymphangiectasis; WHIPPLE'S disease; and neoplasms of the SMALL INTESTINE.