Lactic Acidosis
A condition caused by a buildup of lactate, a cellular waste product, in the blood. Symptoms, if any, may include stomach and breathing problems and general weakness. Severe, untreated lactic acidosis can be life threatening. Increased lactate levels, often combined with hepatic steatosis, may occur in HIV-infected individuals taking NRTIs.
See Also:   Hepatic Steatosis

LAS
See: Lymphadenopathy Syndrome

Latency
The time period when an infectious organism is in the body but is not producing any noticeable symptoms. In HIV disease, latency usually occurs in the early years of infection. Also refers to the period when HIV has integrated its genome into a cell's DNA but has not yet begun to replicate.

Lentivirus
A subgroup of the retrovirus family that includes HIV. Lentiviruses are characterized by a long time period between infection and the onset of symptoms.
See Also:   Retrovirus
                   Incubation Period

Lesion
An area of the body where tissue is abnormal, such as an infected patch or sore on the skin.

Leukocytes
See:    White Blood Cells

Leukocytosis
An abnormally high number of white blood cells in the blood. This condition usually occurs during infection or inflammation.
See Also:   White Blood Cells

Leukopenia
A lower than normal number of white blood cells.

Leukoplakia
See:    Oral Hairy Leukoplakia

LGV
See: Lymphogranuloma Venereum

LIP
See: Lymphoid Interstitial Pneumonitis

Lipid
Any member of a chemical group of fats or fat-like substances.

Lipid Profile
A group of blood tests that are often ordered together to evaluate an individual's risk for heart disease or stroke. These tests include measurement of total cholesterol, HDL-cholesterol ("good" cholesterol), LDL-cholesterol ("bad" cholesterol), and triglycerides.
See Also:   Cholesterol
                   Triglycerides
                   Hyperlipidemia

Lipoatrophy
Loss of body fat from particular areas of the body, especially the arms, legs, face, and buttocks. Lipoatrophy is a potential side effect of some NRTIs.

Lipodystrophy
A problem with the way the body produces, uses, and distributes fat. Lipodystrophy is associated with certain anti-HIV drugs. HIV-related lipodystrophy includes the body changes known as "buffalo hump" and "protease paunch."

Lipohypertrophy
Also known as hyperadiposity. Abnormal buildup of fat, particularly in the breasts, on the back of the neck and upper shoulders ("buffalo hump"), deep within the abdomen ("protease paunch"), or in fatty growths known as lipomas. Lipohypertrophy may occur with the use of some PIs and NRTIs.
See Also:   Lipodystrophy

Liver Function Tests
Blood tests that measure the levels of liver enzymes (proteins made and used by the liver) to determine if the liver is working properly. The liver enzymes that are routinely measured as part of liver function tests are aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyltransferase (GGT), serum glutamic oxaloacetic transaminase (SGOT), and serum glutamic pyruvic transaminase (SGPT). Increased levels of these enzymes indicate that the liver has been damaged.
See Also:   Hepatotoxicity

Log
This mathematical term represents a change in value of what is being measured by a factor of 10. Changes in viral load (the amount of HIV in the blood) are often reported as logarithmic or "log" changes. 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.

Long-Term Nonprogressors
People who have been infected with HIV for a number of years (usually at least 7), but have had stable CD4 cell counts of 600 or more, no HIV-related diseases, and no need for anti-HIV therapy.

Lumbar Puncture
See:    Spinal Tap

Lymph
A clear, slightly yellow fluid that carries disease-fighting white blood cells from the blood to and from body tissues.

Lymph Nodes
Very small organs of the immune system that are located throughout the body. Lymph fluid that bathes body tissues is filtered through lymph nodes as it carries white blood cells to and from the blood.
See Also:   Lymph
                   Lymphadenopathy Syndrome

Lymphadenopathy Syndrome (LAS)
Swollen, firm, and possibly tender lymph nodes. The causes range from infection such as HIV, the flu, or mononucleosis to lymphoma (cancer of the lymphoid tissue).
See Also:   Lymph Nodes

Lymphocyte
A type of infection-fighting white blood cell found in the blood, lymph, and lymphoid tissue.

Lymphocyte Proliferation Assay
A laboratory test that measures the ability of lymphocytes (infection-fighting white blood cells) to recognize an antigen and make more copies of themselves (proliferate) in response to the antigen encounter.
See Also:   Antigen

Lymphogranuloma Venereum (LGV)
A sexually transmitted disease (STD) caused by a species of the chlamydia bacterium. It is characterized by genital lesions and swelling of lymph nodes in the groin.
See Also:   Chlamydia

Lymphoid Interstitial Pneumonitis (LIP)
A lung disorder that causes hardening of the parts of the lung that aid in oxygen absorption. The cause of LIP is unknown, and there is no clear treatment. LIP is an AIDS-defining condition in HIV-infected children.

Lymphokines
Cytokines (chemical messengers that affect the immune response) secreted by white blood cells.
See Also:   Cytokines

Lymphoma
Cancer of the lymphoid tissues. Some types of lymphomas, such as non-Hodgkin's lymphoma and Hodgkin's disease, are associated with HIV infection.

Lymphopenia
A lower than normal number of white blood cells.

Lymphoproliferative Response
An immune system response that results in a rapid rise in the number of white blood cells.

Lysis
The destructive breaking apart of a cell.