Human T-Lymphotropic Virus 1-Induced Skin Diseases at a Glance
- An estimated 10–20 million people are infected by human T-cell lymphotropic virus type 1 (HTLV-1) worldwide, with endemic pockets of high prevalence in Southern Japan and the Caribbean islands.
- Infective dermatitis is a recalcitrant form of eczema occurring in HTLV-1-infected children in the Caribbean.
- Adult T-cell leukemia (ATL) shows monoclonal HTLV-1 provirus integration in tumor cells and occurs in four clinical variants, all of which tend to show skin involvement:
- Smoldering ATL—5% of all cases.
- Chronic ATL—15% of all cases.
- Lymphoma-type ATL—20% of all cases.
- Acute ATL—60% of all cases.
- The prognosis of lymphoma-type and acute ATL is very poor despite chemotherapy, with a projected 4-year survival of 5%.
The first known pathogenic human retrovirus was isolated in 1980 from the lymphocytes of a patient with cutaneous T-cell lymphoma (CTCL) by Poiesz and coworkers.1 Independently, Miyoshi and co-workers later isolated an identical retrovirus from a Japanese leukemia patient.1 The name human T-cell leukemia virus type 1 (HTLV-1) is used now for all isolates previously called adult T-cell leukemia virus in Japan and HTLV in the United States.
An estimated 10–20 million individuals are infected by HTLV-1 worldwide,2–4 with an endemic pattern in Southern Japan, the Caribbean islands, and some countries in equatorial Africa. In some of these locations, most notably the Japanese islands Shikoku, Kyushu, and Okinawa, the seroprevalence reaches 36%.2–4 Small clusters of HTLV-1/HTLV-2 seropositive populations have been reported in restricted areas in South America, among Australian aborigines, and in the Middle East.2–4 In the United States and Europe, the incidence of HTLV-1 infection is below 0.1%, and clusters are found predominately among immigrants from endemic areas, especially those from the West Indies and Africa.2–4
Sexual intercourse is the main mode of horizontal transmission of HTLV-1.2–4 In vertical transmission, breast-feeding plays a more important role than perinatal or intrauterine transmission.2–4 Parenteral transmission of HTLV-1 is also possible, and approximately one-half of patients who received transfusions from an HTLV-1-infected donor seroconvert,2–4 however, the transmission risk by blood transfusion in low prevalence countries is minimal.4,5 Transfusion-mediated HTLV-1 infection in Japan has been virtually eliminated by mass screening of donated blood. In contrast to blood transfusions, cell-free, fresh, frozen plasma appears not to be infectious.5 Parenteral transmission via needle sharing very likely accounts for clusters of HTLV-1/HTLV-2 seropositivity in intravenous drug users in certain areas of the United States and Europe.6
HTLV-1 together with HTLV-2, a virus that has not yet been clearly associated with any human disease, and bovine leukemia virus form their own genus within family Retroviridae.2 Many strains of HTLV-1 have been isolated in different areas of the world, including the United States, the Caribbean islands, Africa, and Japan.3 The overall nucleic ...