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Indolent T cell lymphoproliferative disorder of the gastrointestinal tract or Indolent T cell lymphoproliferative disorder of the GI tract is a rare and recently recognized disorder in which mature T cell lymphocytes accumulation abnormally in the gastrointestinal tract. This accumulation causes various lesions in the mucosal layer lining the GI tract. Individuals with ITCLD-GT commonly complain of chronic GI tract symptoms such as nausea, vomiting, diarrhea, abdominal pain, and rectal bleeding.
Carbonnell et al. first described a case of an indolent GI tract lymphoproliferation disorder in 1994 and defined the lymphocytes involved in it to be T cells expressing the CD4 glycoprotein on their surface membranes. Subsequent studies reported on patients who had a similar indolent GI tract disorder that involved T cells which expressed either the CD4, CD8, or neither surface membrane glycoprotein. The disorder resembled certain aggressive GI tract lymphomas and was variably termed indolent lymphoma or indolent T cell lymphoproliferative disorder of the gastrointestinal tract. However, the disease differed from the aggressive lymphomas which it mimicked in having a prolonged and usually non-progressive course. Furthermore, the disorder's lesions consisted of normal-appearing T cells that proliferated very slowly and usually caused little or no tissue destruction. In 2017, the World Health Organization provisionally classified ITCLD-GT as an extranodal , indolent disorder in which various subtypes of T cells proliferate in the GI tract.
While usually acting like a benign disease, ITCLD-GT has malignant features: 1] its normal-appearing T cells are clonal in nature, i.e. descended from a single cell; 2] these T cells may contain genetic abnormalities that are known to occur in and contribute to the development of very aggressive lymphomas; and 3] ITCLD-GI, after many years of indolent behavior, may progress to an aggressive lymphoma. Thus, ITCLD-GT can act as a premalignat disorder. Nonetheless, most cases of it run an indolent, non-malignant course and when mistakenly treated as an aggressive lymphoma, do not responded to standard chemotherapy treatments. The disorder has also been mistaken for, and found unresponsive to therapies that treat inflammatory or autoimmune bowel diseases. Clinically, ITCLD-GT must be distinguished from the malignant, inflammatory, and autoimmune bowel diseases that it mimics in order to avoid useless and potentially harmful therapies.