Down syndrome (DS) is a common genetic condition affecting 1 in every 700 births. DS occurs when a child is born with an extra copy of chromosome 21. Down syndrome is also called trisomy 21, because this extra copy means a person has three copies of chromosome 21 instead of just two.

The extra chromosome and other genetic abnormalities in Down syndrome put affected children at risk for medical problems, such as gastrointestinal issues, congenital heart defects, hearing problems, and leukemia (blood cancer).

Children with DS are 10 to 30 times more likely to have leukemia — specifically, acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL) — compared to children in the general population. Children with DS are less likely to develop solid tumors, such as in cancers of the bone, organs, or other tissues.

Leukemogenesis and the Development of Leukemia

Leukemogenesis refers to the genetic mutations that happen in children which can lead to the development of leukemia. In children with DS, the first genetic abnormalities occur while they are still growing as a fetus and include inheriting an extra copy of chromosome 21 and mutations in the GATA1 gene. The GATA1 gene is responsible for making the GATA1 protein, which is important for normal development of blood cells. A person with a mutated version of this gene can develop blood disorders and diseases such as leukemia.

Read more about the connection between leukemia and down syndrome here.

Transient Myeloproliferative Disorder

The combination of these two mutations can also lead to a condition known as transient myeloproliferative disorder (TMD). TMD is a preleukemia condition that develops within the first month of life.

Roughly 30 percent of newborns with DS will develop TMD. Most cases will go away on their own without treatment, but 25 percent of children with TMD will go on to develop acute megakaryoblastic leukemia (also known as acute megakaryocytic leukemia or AMKL) or acute myelodysplastic syndrome (MDS). Both of these conditions may also be known as myeloid leukemia of Down syndrome (ML-DS).

Acute Myeloid Leukemia and Down Syndrome

Leukemia is the most common cancer in children and teenagers, making up almost 30 percent of childhood cancers. Typically, ALL is more common in children than AML, but in children with DS, the opposite is true. Children with DS are 150 times more likely to develop AML than other children. AMKL is a rare subtype of AML, and the risk is increased 500-fold for children with DS compared to children without DS.

Children with DS who have AML tend to respond better to treatment than children without DS. Several factors may contribute to the better treatment response, including the subtype of leukemia. Children with DS also respond better to the chemotherapy drug cytarabine, due to genetic changes in how their body processes the drug.

Acute Lymphoblastic Leukemia and Down Syndrome

Children with DS are 33 times more likely to develop ALL when compared to children without DS. The most common types of childhood ALL affect T cells and B cells, which are specialized cells in the immune system that fight infections and make antibodies.

Children with Down syndrome and ALL do not respond as well to treatment as those without DS. Chemotherapy does not appear to be more effective in children with DS and ALL, as it is in those with DS and AML. In addition, other genetic mutations may play a role in how well treatment works. For example, about 20 percent of ALL cases in children with DS have a mutation in the Janus kinase 2 (or JAK2) protein, and 60 percent have too much of another protein, cytokine receptor-like factor 2 (or CRLF2).

Talk With Others Who Understand

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