Adult T-cell Leukemia Lymphoma Facts

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Last updated and reviewed on: July 16, 2026

What is Adult T-cell Leukemia / Lymphoma?

Adult T-cell leukemia/lymphoma (ATL) is a rare and aggressive type of cancer of the immune system's own T-cells. It is caused by the human T-cell lymphotropic virus type 1 (HTLV-1). The disease is characterized by the proliferation of malignant T-cells in the lymph nodes, blood, and other organs, leading to symptoms such as skin lesions, lymphadenopathy, hepatosplenomegaly, hypercalcemia, and immunosuppression.

Types of Adult T-cell Leukemia / Lymphoma

There are four recognized clinical subtypes of ATL, which are classified based on the severity and progression of the disease. These include:

  • Acute ATL: This is the most aggressive form of the disease, characterized by a rapid increase in abnormal T-cells, and severe symptoms including high calcium levels, organ damage, and frequent infections.

  • Lymphoma-type ATL: This subtype is similar to the acute type but primarily involves the lymph nodes.

  • Chronic ATL: This form is less aggressive than the acute and lymphoma types. Patients with chronic ATL may live for several years with the disease.

  • Smoldering ATL: This is the least aggressive form of ATL. Patients with smoldering ATL have few symptoms and the disease progresses slowly.

Why do people get Adult T-cell Leukemia / Lymphoma?

ATL is primarily caused by infection with the human T-cell lymphotropic virus type 1 (HTLV-1). HTLV-1 is a retrovirus that is spread through contact with bodily fluids, including blood, semen, and breast milk. Once inside the body, the virus can integrate into the DNA of T-cells, where it can cause the cells to grow and divide uncontrollably, leading to cancer.

However, not everyone who is infected with HTLV-1 will develop ATL. It is estimated that only about 5% of people with HTLV-1 infection will develop ATL, usually several decades after the initial infection. Factors that may increase the risk of developing ATL in people with HTLV-1 infection include a high viral load, a family history of ATL, and certain genetic factors.

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