Leukemia

Leukemia is a blood cancer, specifically of our white blood cells (WBCs) (a.k.a. “leukocytes”), which are the major component of our immune system.  There are different types of WBCs (see link, and diagram below), thus there are different types of Leukemia, which can be either acute or chronic.  But even though the Leukemias are diseases of WBCs, the 2 other types of blood cells are also affected: Red Blood Cells (RBCs) and Platelets.

We see above that our primordial original Stem Cell in the bone marrow produces subsets: Myeloid Stem Cells and Lymphoid Stem Cells; both produce types of WBCs.  Most granulocytes are Neutrophils, the main actor of innate immunity, our first line of defense to immediately attack and destroy anything that enters our body like germs, splinters, etc. (see also link WBCs).  Lymphocytes comprise our adaptive immunity, which can remember germs that have previously invaded us, then produce antibody and other long-term protection from future infection. 

The Leukemias can be very complex; there are many different types, and all have additional sub-types.  Here we briefly outline the two main types: Myelogenous and Lymphocytic (see diagram above).  Either can be Acute or Chronic.  So the most common Leukemias are:

• Acute Myelogenous Leukemia (AML)
• Acute Lymphocytic Leukemia (ALL)
• Chronic Myelogenous Leukemia (CML)
• Chronic Lymphocytic Leukemia (CLL)

Acute Leukemias  (AML and ALL)

Similarities  —  Patients with AML & ALL may have the same symptoms.  These include:

• Fevers
  • In AML, fever is usually from infection (maybe serious)
  • In ALL, fever may be from the leukemia itself
• Shortness of breath (from Anemia)
• Bruising or bleeding (from low Platelets)
• Fatigue

Diagnosis can usually be suspected from a basic lab test Complete Blood Count (CBC), but must be confirmed by a bone marrow biopsy.  The latter is crucial for determining the subtype of AML or ALL, which guides choice of treatment and suggests the prognosis.  Most patients require intensive chemotherapy initially (“induction”), then ongoing chemotherapy courses.  Some benefit from bone marrow transplants, which might cure the disease but may themselves run a 10% risk of death.

Differences  — 

• AML is much more aggressive than ALL.  Patients may die soon without treatment
• Sepsis and Neutropenia (low neutrophils) occur more often in AML.
  • Normal Neutrophil count is 2,000-6,000
  • <1,000 raises concern; <500 is dangerous; <200 critical
• ALL is much more common <18 years-old, while half of AML patients are >65
  • For both, the older the patient, the less successful treatment
• Swollen lymph nodes, large liver, swollen spleen suggest ALL

Chronic Leukemias (CML and CLL)

CML and CLL involve different types of WBCs: granulocytes (esp. Neutrophils) and Lymphocytes, respectively (see above diagram, also WBCs).  Still, they have many Similarities:

• Both tend to occur at older age; half of CML patients are >60 at time of diagnosis, with CLL half are >70.
• Both tend to be discovered accidently when a CBC blood test is drawn for other reasons, and shows obvious abnormalities:
  • Very high Neutrophil count for CML, very high Lymphocyte count for CLL
• While many patients have no symptoms at time of diagnosis, some may have weight loss, drenching sweats, fatigue, fevers
• Both CML and CLL may cause enlargement of liver and/or spleen
• Both tend to last for years without symptoms before suddenly becoming worse
• Both can be managed well with treatment, which does not require the intensive type of chemotherapy with many side effects as is given for acute leukemias (AML and ALL).

Differences between CML and CLL:

• Complete Blood Count (CBC):  With CML, there are very high neutrophil counts; also maybe high eosinophils, basophils, and platelets too.  With CLL, lymphocytes are very high; there may be low platelets (never with CML)
• CML usually requires a bone marrow biopsy to confirm diagnosis and plan treatment; CLL usually does not
• CLL often causes many swollen lymph nodes
• CLL may occasionally cause an exaggerated skin reaction to bee stings or mosquito bites, providing a clue to diagnosis

Once again, in contrast with Acute Leukemias, the treatment for CML and CLL is not toxic, and is often very effective.