Information for Adults | Understanding ALL

Understanding ALL

Figure 1

ALL stands for Acute Lymphoblastic Leukaemia (also known as Acute Lymphocytic Leukaemia or Acute Lymphoid Leukaemia). ALL is a form of blood cancer affecting the lymphocytes, a type of blood cell (Figure 1) that fights infection.

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Is ALL common?

Adult ALL is classified as a rare disease and accounts for only ~20% of adult leukaemia cases.[1]

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What happens in ALL?

Normally, lymphocytes have a set lifespan. They grow, multiply and die in a controlled manner after which they are replaced by a new cell.

In ALL, a single lymphocyte cell in the bone marrow is mutated or changed allowing it to grow and divide in a rapid and uncontrolled manner. The resulting 'abnormal' cells are usually 'immature' and known as (lympho-) blast cells which is why the condition is called acute lymphoblastic leukaemia.

These abnormal cells fill the bone marrow and eventually affect its ability to produce all types of red and white blood cells causing:

  • An increased risk of infection due to a reduced number of functioning white blood cells
  • Anaemia and fatigue due to a reduced number of red blood cells
  • Bleeding and bruising due to a reduced number of platelets

The progression of ALL (Figure 2) can be very rapid (known as 'acute'). Mutated cells can spread into different tissues including the fluid in the spine (cerebrospinal fluid) which is the reason why early diagnosis and treatment is so important.

bones stages

Figure 2: The progression of ALL. Normally the bone marrow produces a combination of white blood cells (to fight infection), red blood cells (to carry oxygen) and platelets (to stop bleeding). A single abnormal ALL cell can multiply and fill the bone marrow, reducing its capacity to produce normal blood cells. Reduced numbers of white blood cells make you more susceptible to infection while reduced production of red blood cells (known as anaemia) will make you feel fatigued, and reduced platelets will make you more prone to bleeding and bruising. In later stages of the disease, the abnormal ALL cells can spread to other organs such as the liver or central nervous system. Your doctor will know all of this and select the most appropriate treatment to destroy all of the ALL cells in your body.
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What are white blood cells?

White blood cells are the immune cells of the body that fight against infections. There are two major groups of white blood cell, lymphocytes and phagocytes:

  • Lymphocytes
    • T cells – directly kill infections
    • B cells – produce antibodies, a type of protein that binds to infections and marks them for destruction by the T cells
  • Phagocytes
    • Monocytes – phagocyte cells that divide and mature into macrophages in response to infection
    • Macrophages – specialised cells present within tissues that digest infections and help to activate the lymphocytes

All of the white blood cells are produced by the bone marrow, the soft tissue inside the long bones of the body. The bone marrow is also responsible for producing red blood cells that carry oxygen around the body and platelets which are small pieces of cells that stop bleeding by blocking damaged blood vessels.

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What causes ALL?

No one really knows what causes ALL. Exposure to high-dose radiation is the only clearly identified risk factor. Other less clear risk factors include; being white, male, aged older than 70 years and having certain genetic disorders such as Down's syndrome.

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Are there different types of ALL?

There are many different types of ALL that can be distinguished by the type of cell (such as a B cell [Figure 3]) involved and genetic factors (such as chromosome abnormalities [see 'What is a chromosome?' and 'What is the Philadelphia chromosome?']. The majority of adult ALL cases begin with the mutation of an immature B cell (75% incidence), with mutations in T cells (20% incidence) or more mature B cells (5% incidence) occurring less frequently.[2] New genes are constantly being discovered and treatments are advancing allowing doctors to personalise treatment to attack the abnormal ALL cells specifically in each patient [see 'What factors will affect my treatment and prognosis'].


Figure 3
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What is a chromosome?

Chromosomes are the structures that hold our genetic information in the form of DNA (deoxyribonucleic acid), the building blocks of life. Chromosomes are found within cells contained in a structure called the nucleus. Humans have 23 pairs of chromosomes (one of each pair comes from each parent). Chromosome abnormalities can be associated with certain types of ALL; your doctor will specifically tailor your treatment to fit the type of ALL you have.

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What is the Philadelphia chromosome?

The Philadelphia chromosome was identified in another type of leukaemia called chronic myelogenous leukaemia (CML) but is also found in around 20% of ALL cases. It has traditionally been considered as a marker of poorer prognosis, although the availability of newer drugs such as imatinib mesylate has helped to improve patient outcomes.[3]

The Philadelphia chromosome is a genetic abnormality that involves the movement of genetic material between chromosomes 9 and 22.

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Are my children/siblings at risk?

If you have an identical twin, they are at an elevated risk of also developing ALL and should consult a doctor to monitor their condition. There is no direct evidence demonstrating an increased risk for siblings (non-twins) or children of a patient with ALL. However, if you are concerned and have a history of ALL in your family please consult your doctor who should be able to help.

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Am I contagious?

No, you are not contagious. ALL is not an infectious disease and cannot be caught by people you come into contact with.

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References

[1] Cancer Treatment Centers of America – http://www.cancercenter.com

[2] Leukaemia Research Foundation – http://www.lrf.org.uk

[3] Souhami R and Tobias J. Cancer and its management. Wiley-Blackwell 2005, 5th edition

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