In this lecture, we will review leukemia in children.
So, leukemia is the malignant transformation
and proliferation of hematopoietic cells.
So we have acute leukemia which is a clonal expansion of immature precursors,
and we have chronic leukemia
which is mature bone marrow components that are then becoming clonal.
So, symptoms can occur from a lack of normal bone marrow cell production
or from accumulation of malignant cells in tissues
that otherwise shouldn’t have them.
So let’s go through the epidemiology of leukemia in children.
It is the most common pediatric malignancy.
Thirty percent of all newly diagnosed children with cancer have leukemia,
and boys typically get it a little bit more than girls.
So we break down leukemia typically in kids into four major types.
By far and away the most common types are the first two.
Let’s go through these. First we have acute lymphoblastic leukemia.
Acute lymphoblastic leukemia or ALL is very common in kids.
It’s a proliferation of B and T cell lymphocyte precursors,
like you can see here.
It typically happens in children between the age of 2 and 5
and again boys a little more commonly than girls.
Caucasians are at greatest risk for ALL.
Comparing that to AML which is acute myelogenous leukemia.
AML is a clonal proliferation of myeloid precursors.
So there are many subtypes of AML
based on the morphology of the cells that are growing
and the cytogenic translocations that have occurred
which cause these cells to become clonal in nature.
There is a generally bimodal incidence
in terms of when children get this disease.
There’s one peak in little, tiny kids under 2 years of age
and then again at adolescence.
And this for AML, unlike ALL, the rate in boys and girls is about the same
and this is associated with some toxic exposures,
also some genetic predispositions.
For example, children with Down syndrome
have a 50-fold increase in their risk for AML,
remember that, Down syndrome and AML, strong association.
Now we would switch gears to chronic disease
and this is chronic myelogenous leukemia which is less common in kids.
This is an uncontrolled growth of myeloid cells
and the incidence increases through childhood and adolescence.
Often these patients have a fusion protein, the BCR-ABL gene.
This constitutively activates tyrosine kinase,
the mutation in this translocation
between chromosome 9 and chromosome 22
causes a continuously on activation of tyrosine kinase.
And lastly, we’ll talk very briefly about the very mild form of leukemia
which is juvenile myelomonocytic leukemia or JMML.
JMML is very rare.
It’s usually diagnosed before the age of 3
and the etiology is basically unknown.
It is associated, however, with a few genetic conditions like Down syndrome,
neurofibromatosis, Li-Fraumeni syndrome, and Fanconi anemia.