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ACUTE LYMPHOCYTIC LEUKEMIA

ACUTE LYMPHOCYTIC LEUKEMIA (ALL) -



also known as Acute Lymphatic, Acute Lymphoblastic, or Acute Lymphogenous Leukemia - is now considered the most curable of all major forms of leukemia in children. It is the leading form of leukemia in children, representing approximately 85 percent of leukemia in patients under age 21.

ALL primarily attacks patients between two and ten years of age. However, it can and does strik at any age. A substantial proportion of older adolescents and adults also develop the disease, with the number of cases again rising around 50 and climbing steadily with increasing age.

Overall the attack rate is 1.1 person per one hundred thousand population, or, in children between two and ten years of age, 4.4 per one hundred thousand. In effect, more than 2,000 children will be diagnosed with ALL this year. Cases will, in all liklihood, continue to increase at a rate commensurate with the increase in population.

ALL has been reported in all races and geographic areas. Its overall incidence is fairly equal among males and females, but somewhat less common among oriental and black populations.

WHAT IT IS



Acute lymphoctyic leukemia is a malignant disorder involving the production of immature white blood cells of the lymphocyte series. The net effect is bone marrow, the bloodstream, and lymphatics. Less commonly, accumulations are seen in certain nervous system sites, like the central nervous system and gonads.

Perhaps ALL can best be understood by first becoming familiar with the function, composition, and cell growth activity of healthy blood, and with some general information which is common to all forms of leukemia.

BLOOD FUNCTIONS AND COMPOSITION



The blood is a vital organ which supplies oxygen, food, and other essential nutrients,hormones, and chemicals to cells throughout the body. It serves as one of the body's most effective defenses against infection, and also assists in the removal of toxins and other waste materials.

Whole blood is made up of many components, with each component performing a specific role in the blood's overall functions. The three main elements involved in the process are red cells, clotting cells (or platelets) and white cells, all of which circultate through the bloodstream in a clear protein-rich medium referred to as plasma or serum.

RED BLOOD CELLS

(Erythocytes) contain hemoglobin, an iron-rich protein which picks up oxygen as the blood passes through the lungs, transports it, and releases it to organs and tissues throughout the body. Carbon dioxide, produced by metabolizing cells, is in turn pikced up by the red cells at the tissue level and transported to the lungs for elimination and reoxygenation. Red cells live approximately 120 days. A shortage of these red blood cells, a condition known as anemia, can cause weakness, dizziness, shortness of breath, headaches, and irritability.

CLOTTING CELLS

(Platelets) are tiny disc-shaped cells which help prevent abnormal or excessive bleeding by plugging blood vessels and forming clots. A deficiency of platelets can cause bleeding into any organ or tissue, such as the skin. Unexplained or excessive bruising is characteristic of platelet deficiencies.

WHITE BLOOD CELLS

(Leukocytes) play a major role in defending the body against disease-producing bacteria, viruses, fungi and parasites. There are three main types of leukocytes, with each type performing a specific infection-fighting function:

Monocytes defend the body against bacterial infection and ingest aging and degeneration blood cells.

Granulocytes include neutrophils, eosinophils and basophils. Neutrophils are the predominant type, counting for about 60 percent of all circulating white blood cells. They combat infection by rapidly increasing in number, engulfing and destroying foreign substances. They then die and are, in turn, ingested by monocytes. Once an infection is under control, production of neutrophils returns to the original pre-infectioin count and steady state. Eosinophils and basophils play roles in modulating the immune response and maintaining an intact blood vessel wall.

Lymphocytes patrol the blood and lympatic systems, the latter a filtering and drainage system consisting of a milky-colored fluid which circulates through a network of glands, picking up waste material and depositing it into the bloodstream - and the lymphoid organs like the spleen, thymus and thyroid glands, and the lymph nodes.

There are two main types of lymphocytes which combine forces to create a complex interaction designed to regulate the immune response. T cells and natural killer subsets attack virus-infected and cancer cells. B cells produce and release antibodies, protein substances which bind to infectious agents and help prevent them from doing damage.

A deficiency in any type of normal white blood cell may result in an increased susceptibility to infection, as well as in a reduced resistance to any number of diseases.

BLOOD CELL GROWTH



The blood, like all human tissues and organs, is composed primarily of cells which are developed enough to perform efficiently. The circulating red, white and clotting cells mature and enter the bloodstream through the blood cell growth process known as hematopoiesis. This process begins with the production of immature cells - initially in the cell islands and then in the liver and spleen before becoming established in the marrow spaces. A small percentage of cell production takes place in the lymph nodes. The majority of cells, including those involved in ALL, originate in the bone marrow - the spongy meshwork which fills the cavities of the large bones. They continue to develop in either the bone marrow or the thymus gland. Leukemic cells that originate int he thymus gland usually migrate to and then grow in the marrow space.

Human blood cell growth usually occurs in an orderly fashion. Every tissue or organ contains within itslef a pool of immature, or undifferentiated, cells known as stem cells. These cells begin a process of division and differentiation which results in the developlment of mature cells to replace those which have become old and worn out. The immature cells involved in blood cell production are called pluripotent stem cells, and, as such, contain the characteristics of all the major blood cell lines. These cells divide, either reproducing themselves exactly or producing more specialized cells which contain the characteristics of only one of the two major cell lines. One of these lines is known as the myeloid line and consists of the red cells, platelets and white cells called monocytes and granulocytes. The other is the lymphoid line which gives rise to the lymphocytes. This reproduction process continues with cell characteristics becoming increasingly defined with each division, until "committed" cells, which eventually evolve into one specific cell type, are produced. As these cell types mature, they are released into the bloodstream at a rate consistent with the death of old cells.

With the exception of T-lymphocytes, blood cells are not released from the bone marrow until they are fully mature. T cells leave the bone marrow at a relatively immature state and mature in the thymus gland before they enter the bloodstream. Normally, immature stem cells or "blasts" are only present in the circulating blood in very small numbers. A relatively small amount of these cells can be found in the bone marrow and thymus gland because they are still involved in the growth process. However, even in these two areas, "blasts" should never constitute more than five percent of the total cell population.

The entire blood cell growth, maintenance and destruction cycle is a highly efficient and orderly process. The abnormal and excessive reproduction of any type of cell obviously disrupts the delicate balance necessary to sustain the body's general state of health and well-being.

LEUKEMIA



The term leukemia is derived from Greek and means "white blood". Leukemia is characterized by failure to produce mature white blood cells. The cells overgrow uncontrollably, become too numerous and crowd out existing healthy cells. These abnormal white cells, referred to as "blasts" overpopulate the bone marrow and spill into the bloodstream.

Leukemic cell over-population impairs the marrow, which is then unable to maintain production of sufficient numbers of red cells, platelets and white cells. The net effect is anemia, bleeding and impaired infection-fighting capabilities.

As leukemic cells circulate throughout the blood and lymphatic systems, they infiltrate vital organs like the lungs, kidney, spleen and liver, which in turn become impaired, and malfunctioin. Often these organs become enlarged. Leukemic cells may even invade the tissues surrounding the brain and spinal cord by crossing the blood-brain barrier, a system of tightly meshed cells, which helps to protect the central nervous system.

As the disease progresses, blast cells flood the entire system, rendering a patient susceptible to fatigue and excessive bleeding, and causing every minor infection or injury to become a potentially hazardous condition.

Untreated, death occurs from bleeding, form the spread of infection or from organ failure.

There are two major forms of acute leukemia:

*Lymphocytic Leukemia which affect immature white cells of lymphoid lineage.

* Myelocytic Leukemia which involves the myeloid or precursor line.

In the chronic form of these diseases, the cells have reached a more mature stage of development.

Acute Lymphocytic Leukemia, then, specifically refers to a malfunction in the production of immature lymphocytes which would normally develop into mature T or B cells.

ALL consists of the following subtypes or groups:

*Common ALL, referred to as cALLa , the common ALL antigen, is a B-lineage lymphocyte with surface antigeneic markers, referred to as CD-10 in keeping with the international white cell nomenclature system. It occurs in approximately 71 percent of children and 50 percent of adults with ALL.

*Pre-B-Cell ALL is a less common B-cell lineage malignancy. It is antigeneically a CD-19 marker and occurs in 12 percent of all children with ALL.

*T-Cell ALL occurs primarily in older adolescents and young adults, with a slightly higher incidence among males. Overall, the incidence is approximately 12 percent. It affects immature stem cells which exhibit T-lineage surface markers characteristic of the T-cell line of development.

Even less common types include mixed lineage acute leukemia, which has both lymphoid and myeloid markers and Ph'ALL. Ph'ALL may represent the "blast phase" of a previously undetected chronic myelocytic leukemia, but some adults and children have Ph'ALL which is not related to chronic myelocytic leukemia.

*Null-Cell, or Undifferentiated ALL are essentially outmoded terms. As diagnostic studes improve, identification of the various subtypes has eliminated the use of generic or undifferentiated terminology.

These biological features of the leukemic cell are important prognostic factors. Identification also includes histologic aspects by the French-American-British classification (L1, L2, L3), histochemical staining (Tdt, PAS) surface markers (CD+), as well as both quantitative chromosomal analyses.

ALL is a life-threatening disease. Its advance is rapid, and, left undiagnosed and untreated, life expectancy is less than one year. However, treatment has extended and improved the quality of life for the majority of patients, many of whom appear to be cured.

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Here's What You'll Find in these pages

  • The index to all of the links for Marissa's Story
  • ALL (this page) - Part 1 of an explanation of exactly what Acute Lymphocytic Leukemia is
  • ALL Part 2 - Part 2 of the explanation of what Acute Lymphocytic Leukemia is
  • Marissa's Story - Part 1 of how it came about that Marissa was diagnosed with ALL
  • Marissa's Story Part 2 - Part 2 of Marissa's struggle with ALL
  • Photos - Marissa's Photo Album
  • Photos 2 - Part 2 of Marissa's Photo Album
  • Photos 3 - Jessica's Photo Album
  • Photos 4 - Randy's Photo Album

LINKS TO OTHER PAGES OF MARISSA'S STORY

Marissa's Story Homepage
Part 2 of an explanation of Acute Lymphocytic Leukemia
Part 1 of Marissa's Story
Part 2 of Marissa's Story
Marissa's Photo Album
Part 2 of Marissa's Photo Album
Jessica's Photo Album
Randy's Photo Album

Email: angelmomt@aol.com