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Lactic Acid Audio (En español)

Acid formed by the breakdown of glucose when oxygen levels in the body are low. The body uses lactic acid for energy.

See Related Term(s): Lactic Acidosis

Lactic Acidosis Audio (En español)

A condition in which lactic acid builds up in the blood. If left untreated, lactic acidosis can be fatal. Symptoms, if any, can include nausea, abdominal pain, muscle ache and weakness, and unintentional weight loss. Lactic acidosis may be caused by advanced HIV infection or antiretroviral (ARV) drugs.

Latent HIV Reservoir Audio (En español)

Also known as: Reservoir

Resting CD4 cells (or other cells) that are infected with HIV but not actively producing HIV. Latent HIV reservoirs are established during the earliest stage of HIV infection. Although antiretroviral therapy (ART) can reduce the level of HIV in the blood to an undetectable level, latent reservoirs of HIV continue to survive. When a latently infected cell is reactivated, the cell begins to produce HIV again. For this reason, ART cannot cure HIV infection.

See Related Term(s): Viral Latency

Latent Tuberculosis Infection Audio (En español)

When a person is infected with Mycobacterium tuberculosis, but the immune system prevents the bacteria from growing. Because the bacteria are inactive, the person does not feel sick and does not have any symptoms of tuberculosis (TB). A person with latent TB infection cannot spread TB to others. Without treatment, latent TB infection can advance to TB disease, especially in people with weakened immune systems.

See Related Term(s): Tuberculosis, Tuberculosis Disease

Leishmaniasis Audio (En español)

A disease caused by the protozoan Leishmania, which is usually transmitted by the bites of infected sand flies. There are four major types of leishmaniasis: cutaneous, diffuse, mucocutaneous, and visceral. Visceral leishmaniasis affects internal organs and is characterized by fever, weight loss, enlargement of the spleen and liver, and a drop in blood cell production with possible anemia. In people with AIDS, visceral leishmaniasis is the most common type, and, if left untreated, it is nearly always fatal.

See Related Term(s): Opportunistic Infection

Lentivirus Audio (En español)

A subgroup of retroviruses, which includes HIV.

See Related Term(s): Retrovirus

Lesion Audio (En español)

Damage or an abnormal structural change to a tissue, organ, or body part because of injury or disease. Examples of a lesion include a wound or an infected or diseased patch of skin.


Also known as: White Blood Cell

Leukocytosis Audio (En español)

An increase in the number of white blood cells. Leukocytosis often occurs during acute infection or inflammation. 

See Related Term(s): White Blood Cell

Leukopenia Audio (En español)

A low or reduced number of white blood cells.

See Related Term(s): White Blood Cell

LGBTQ Audio (En español)

Acronym for lesbian, gay, bisexual, transgender, and questioning.


Also known as: Lymphogranuloma Venereum

Life Cycle Audio (En español)

Also known as: Replication Cycle

The sequence of events required for HIV to replicate. There are seven steps in the HIV life cycle: 1) fusion; 2) reverse transcription; 3) integration; 4) transcription; 5) translation; 6) budding; 7) maturation.

See Related Term(s): Budding, Fusion, Integration, Reverse Transcription, Viral Replication

Linear Gingival Erythema Audio (En español)

Also known as: HIV Gingivitis, Red-Band Gingivitis

A condition in which the edge of the gums near the teeth become red and inflamed. Linear gingival erythema is common with HIV infection.

Lipid Audio (En español)

Fat or fat-like substances found in the blood and body tissues. Lipids serve as building blocks for cells and as a source of energy for the body. Cholesterol and triglycerides are types of lipids.

Lipid-Lowering Agent

Also known as: Statin

Lipid Profile Audio (En español)

Also known as: Coronary Risk Profile

A group of blood tests that measure cholesterol and triglyceride levels. Test results are used to determine a person's risk for heart disease or stroke. High lipid levels may be associated with use of some antiretroviral (ARV) drugs.

Lipoatrophy Audio (En español)

Loss of fat from specific areas of the body, especially from the face, arms, legs, and buttocks. Use of some antiretroviral (ARV) drugs may cause lipoatrophy.

See Related Term(s): Lipodystrophy

Lipodystrophy Audio (En español)

Also known as: Fat Maldistribution

Changes in lipid metabolism and body composition, including accumulation of fat (lipohypertrophy), loss of fat (lipoatrophy), and redistribution of fat. Use of some antiretroviral (ARV) drugs may cause lipodystrophy.

See Related Term(s): Dorsocervical Fat Pad, Lipoatrophy, Lipohypertrophy, Lipoma, Wasting Syndrome

Lipohypertrophy Audio (En español)

Also known as: Hyperadiposity

Abnormal accumulation of fat, particularly within the abdominal cavity, the upper back (buffalo hump), and subcutaneous tissue (peripheral lipomatosis). Use of some antiretroviral (ARV) drugs may cause lipohypertrophy.

See Related Term(s): Lipodystrophy

Lipoma Audio (En español)

Benign (not cancerous) lumps of fat that develop under the skin. Lipomas can develop as a result of lipodystrophy, which may be caused by certain antiretroviral (ARV) drugs.

See Related Term(s): Lipodystrophy

Live Attenuated Audio (En español)

Also known as: Attenuated

A disease-causing virus or bacterium that is weakened in a laboratory so it cannot cause disease (or only mild disease). Live attenuated viruses are often used as vaccines because, although weakened, they can stimulate a strong immune response. However, because of remote possibility that a live attenuated virus could cause disease, people infected with HIV should not receive most live attenuated vaccines.

See Related Term(s): Vaccine

Liver Audio (En español)

The largest organ in the body, located in the upper abdomen on the right side. The liver has many important functions, which include converting food into energy, producing bile (a liquid that helps with digestion), processing drugs and alcohol, removing toxins from the body, filtering blood, and producing blood cells and blood-clotting components.

See Related Term(s): Hepatitis

Liver Function Test Audio (En español)

A group of blood tests used to detect, evaluate, and monitor liver disease or damage. A liver function test measures enzymes, proteins, and other substances that are produced or excreted by the liver, such as alanine aminotransferase (ALT), alkaline phosphatase (ALP), aspartate aminotransferase (AST), gamma-glutamyl transpeptidase (GGT), bilirubin, and albumin.

See Related Term(s): Alanine Aminotransferase, Albumin, Aspartate Aminotransferase, Bilirubin, Gamma-Glutamyl Transpeptidase, Hepatotoxicity, Liver

Localized Audio (En español)

Affecting only a specific or limited part of the body rather than the entire body.

See Related Term(s): Systemic


Also known as: Log10

Log10 Audio (En español)

Also known as: Common Logarithm, Log, Logarithm

A mathematical term used to describe changes in viral load (HIV RNA). For example, if the viral load is 20,000 copies/mL, then a 1-log increase equals a 10-fold (10 times) increase, or 200,000 copies/mL. A 2-log increase equals a 100-fold increase, or 2,000,000 copies/mL.

See Related Term(s): Viral Load, Viral Load Test


Also known as: Log10

Long-Term Nonprogressors Audio (En español)

A small group of people infected with HIV who are able to maintain healthy CD4 counts for many years without antiretroviral therapy (ART).

Lumbar Puncture

Also known as: Spinal Tap

Lymph Audio (En español)

A clear-to-yellowish fluid that circulates throughout the body. In addition to its fluid component, lymph consists of white blood cells (especially lymphocytes) and a small concentration of red blood cells and proteins. As lymph circulates, it picks up unwanted materials, such as bacteria and dead cells, which are then filtered through the lymph nodes. Lymph also supplies mature lymphocytes to the blood.

See Related Term(s): Lymph Nodes

Lymphadenopathy Audio (En español)

Abnormal enlargement of lymph nodes, usually associated with an infection or disease. Lymphadenopathy may also occur as part of a hypersensitivity reaction to certain antiretroviral (ARV) drugs.

See Related Term(s): Lymph Nodes

Lymphatic System Audio (En español)

A network of organs, nodes, ducts, and vessels that produce and transport lymph from the body’s tissues to the bloodstream. The lymphatic system helps to maintain fluid balance in the tissues and blood; to supply nutrients, oxygen, and hormones to cells; to transport fats, proteins, and white blood cells to the blood; and to fight infection and filter out foreign organisms and waste products.

Lymph Nodes Audio (En español)

Very small organs of the lymphatic system. Lymph nodes are located in many areas of the body, mainly in the neck, under the arms, and in the groin. Lymph nodes play a crucial role in the immune system. When lymph is filtered through the lymph nodes, foreign substances are trapped and destroyed by the lymphocytes that line the walls of the lymph nodes.

See Related Term(s): Lymph, Lymphatic System, Lymphocyte

Lymphocyte Audio (En español)

A type of white blood cell. Most lymphocytes can be classified as T lymphocytes (T cells), B lymphocytes (B cells), or natural killer cells. Lymphocytes are found in the blood, lymph, and lymphoid tissue and help the body fight infection.

See Related Term(s): White Blood Cell

Lymphocyte Proliferation Assay Audio (En español)

A laboratory test that measures the ability of lymphocytes to replicate (proliferate) when exposed to an antigen.

See Related Term(s): Antigen

Lymphogranuloma Venereum (LGV) Audio (En español)

A chronic infection of the lymphatic system caused by three strains of the bacterium Chlamydia trachomatis. Lymphogranuloma venereum (LGV) is a sexually transmitted infection. Symptoms include genital or rectal ulcers. LGV may increase the risk for sexual transmission of HIV.

See Related Term(s): Sexually Transmitted Infection

Lymphoid Interstitial Pneumonitis (LIP) Audio (En español)

Inflammation and possible scarring of the tissue that surrounds the air sacs of the lungs (lung interstitium). Symptoms of lymphoid interstitial pneumonitis (LIP) include fever, cough, and difficult breathing (dyspnea). LIP is associated with autoimmune diseases, lymphoproliferative disorders, and certain viral infections, such as HIV or Epstein-Barr virus. LIP is an AIDS-defining condition in children infected with HIV who are 13 years or younger.

See Related Term(s): AIDS-Defining Condition

Lymphoma Audio (En español)

A type of cancer that starts in the tissues of the lymphatic system, including the lymph nodes, spleen, and bone marrow. In people infected with HIV, certain lymphomas, such as Burkitt lymphoma, are AIDS-defining conditions.

See Related Term(s): AIDS-Defining Condition, Lymphatic System

Lymphopenia Audio (En español)

Lower-than-normal number of lymphocytes (a type of white blood cell) in the blood.

Lymphoproliferative Response Audio (En español)

An immune system response that stimulates lymphocytes (a type of white blood cell) to multiply rapidly.

See Related Term(s): Lymphocyte

Lysis Audio (En español)

The breakdown or destruction of cells. Lysis may be caused by chemical or physical damage, such as by drugs or injury, or infection.

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