Leukemia, often colloquially referred to as blood cancer, is a group of cancers of the hematopoietic system. It occurs when white blood cells multiply uncontrollably and disrupt normal blood formation. This disease can affect people of any age, but is more common in children and older adults. Leukemia is a serious diagnosis, but thanks to modern medicine, there are many treatment options available today. In this article, we explain what leukemia is, what symptoms it causes, how it is diagnosed and which laboratory values are crucial.

What is leukemia?

Leukemia develops in the bone marrow, where blood cells are formed. Normally, the bone marrow produces red blood cells (for oxygen transport), white blood cells (for immune defense) and platelets (for blood clotting) in a balanced ratio. In leukemia, this process gets out of control: certain white blood cells, usually immature precursors, multiply unchecked and displace healthy blood cells. As a result, the normal functions of the blood – such as defense against infection, oxygen transport or blood clotting – can no longer be performed properly.

There are various forms of leukemia, which differ according to the course (acute or chronic) and the type of cell affected (lymphatic or myeloid). The most common types include

• Acute lymphoblastic leukemia (ALL): Common in children, rapid progression.
• Acute myeloid leukemia (AML): Often occurs in adults, also acutely.
• Chronic lymphocytic leukemia (CLL): Mostly in older people, slow progression.
• Chronic myeloid leukemia (CML): Can occur at any age, often slow onset.

The causes of leukemia are not always clear. Risk factors include genetic predisposition, exposure to radiation or chemicals, certain viruses or previous bone marrow diseases.

Symptoms of leukemia

The symptoms of leukemia vary depending on the type and stage, often developing rapidly in acute forms and gradually in chronic forms. Typical signs are

• Fatigue and weakness: The body lacks energy due to the lack of red blood cells (anemia).
• Frequent infections: Since functional white blood cells are missing, the immune defense is weakened.
• Tendency to bleed: A lack of platelets leads to bruising, nosebleeds or bleeding gums.
• Fever and night sweats: Common in acute leukemia, often without a recognizable infection.
• Swollen lymph nodes or spleen: Especially in lymphatic leukemias.
• Bone pain: Due to the overproduction of cells in the bone marrow.

Many of these symptoms are non-specific and can also have other causes. Laboratory tests are therefore crucial if leukemia is suspected.

Diagnosis of leukemia

The diagnosis of leukemia often begins with a medical history and physical examination, during which doctors look for symptoms such as pale skin, swollen lymph nodes or an enlarged spleen. The next step is blood tests that reveal abnormalities in the blood count. To confirm the diagnosis, a bone marrow puncture is usually performed, in which a sample is taken from the bone marrow and examined under a microscope. Imaging procedures such as ultrasound or CT can help to assess the spread of the disease.

Laboratory values play a central role, as they make the dysfunction of the hematopoietic system visible and provide indications of the type of leukemia.

Important laboratory values for leukemia

The following laboratory values are particularly important in the diagnosis and monitoring of leukemia:

1. Leukocytes (white blood cells):
   • Meaning: Indicates the number of white blood cells, which is often greatly altered in leukemia.
   • Normal range: 4,000-10,000 per microliter.
   • For leukemia:
     • Acute leukemia: The leukocyte count can be greatly increased (e.g. >50,000) or decreased, as immature cells (blasts) displace the normal cells.
     • Chronic leukemias: Usually significantly elevated, often >20,000, especially in CLL or CML.
   • Special feature: Analysis of the differential blood count (examination of cell types) often shows immature blasts or abnormal lymphocytes.
     
2. Hematocrit and hemoglobin (red blood cells):
   • Significance: Measures the oxygen transport capacity of the blood. A deficiency leads to anemia.
   • Normal range: hemoglobin: men 13.5-17.5 g/dl, women 12-16 g/dl.
   • In leukemia: Often reduced, as the bone marrow does not produce enough red blood cells. This leads to paleness and tiredness.
   • Special feature: The drop can be particularly rapid in acute leukemia.
     
3. Thrombocytes (blood platelets):
   • Significance: Important for blood clotting. A deficiency increases the risk of bleeding.
   • Normal range: 150,000-400,000 per microliter.
   • In leukemia: Frequently reduced (thrombocytopenia), especially in acute leukemia, which leads to bruising or bleeding.
   • Special feature: In chronic leukemia, the number may initially be normal or even elevated.
     
4. Differential blood count:
   • Meaning: Shows the distribution of the different types of white blood cells.
   • In leukemia: Frequently increased proportions of immature cells (blasts) in acute leukemia or abnormal lymphocytes in CLL. A “left shift” (more immature cells) is typical.
   • Special feature: The microscopic examination of a blood smear is often decisive in confirming the diagnosis.
     
5. lactate dehydrogenase (LDH):
   • Significance: An enzyme that is released during cell decay. Elevated values indicate high cell activity.
   • Normal range: 135-225 U/l (depending on the laboratory).
   • In leukemia: Often elevated, especially in acute leukemia, as many cells are destroyed.
   • Special feature: Can also be elevated in other cancers, is therefore not specific.
     
6. Bone marrow examination:
   • Significance: A microscopic analysis of the bone marrow shows the extent to which normal hematopoiesis is disturbed and which cell types dominate.
   • In leukemia: Often shows a high proportion of immature blasts (in acute leukemia >20 %) or abnormal cells.
   • Special feature: Genetic tests (e.g. for chromosomal changes such as the Philadelphia chromosome in CML) can clarify the diagnosis.

Treatment and progression

The treatment of leukemia depends on the type, age and general condition of the patient. Acute leukemias often require immediate chemotherapy to destroy the cancer cells. Chronic leukemias can sometimes be treated with targeted therapies (e.g. tyrosine kinase inhibitors for CML) or a “watch-and-wait” strategy. In severe cases, a stem cell transplant is necessary, in which the diseased bone marrow is replaced with healthy bone marrow.

The course of the disease varies greatly: while acute leukemias quickly become life-threatening without treatment, chronic forms can remain stable for years. The prognosis has improved significantly thanks to new therapies, especially for children with ALL.

Conclusion

Leukaemia is a complex disease of the haematopoietic system characterized by an uncontrolled proliferation of white blood cells. Typical symptoms such as fatigue, infections or bleeding indicate impaired hematopoiesis. Laboratory values such as leukocytes, haemoglobin, thrombocytes and the differential blood count are decisive in making the diagnosis and monitoring the course of the disease. A bone marrow examination provides additional clarity. Thanks to modern diagnostics and therapies, many patients now have a good chance of successful treatment. If leukemia is suspected, rapid medical clarification is essential to ensure the best possible care.

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Gender note. The personal designations used in this text always refer equally to female, male and diverse persons. Double/triple references and gendered designations are avoided for the sake of better readability ected.