Raising a child with Down syndrome (DS) can have its difficulties. The significant risk of developing certain cancers poses additional challenges to families and the DS community.
What is Down Syndrome?
Down syndrome is the presence of extra genetic material from Chromosome 21. According to the CDC, Approximately 1 in every 700 babies is born with DS, making it the most common chromosomal condition in the US.
Alongside certain cancers, research shows DS heightens the body’s susceptibility to a range of health conditions. This includes hypothyroidism, heart defects, hearing loss, vision problems, and certain infections.
A Unique Position
Compared to the general population, people with DS actually have a similar or even a slightly reduced lifetime risk of developing cancer overall, according to various studies. In both children and adults with DS, findings show a decreased risk for many solid tumors – those not containing any liquids or cysts. One exception to this is the higher risk of testicular cancer in males with DS.
Research explaining this found that one particular gene (DSCR1) on Chromosome 21 slows tumor growth by preventing it from making its own blood supply. Since those with DS have an extra copy of DSCR1, this creates a protective effect against solid tumors.
However, this is only one aspect of Down syndrome’s unique genetic differences, and It’s most likely there are multiple contributing factors leading to decreased risk of solid tumors.
On the other hand, individuals with DS have a significantly heightened risk of developing certain types of Leukemias as well as a notable risk increase in testicular cancer, as mentioned before.
Relationship with Leukemia
Down syndrome was first linked to Leukemia in 1930. Since then, it has become “one of the most important leukemia-predisposing syndromes,” a 2010 publication wrote.
Studies estimate individuals with DS are anywhere from 10 to 30 times more likely to be diagnosed with blood cancers than non-DS individuals. In children with DS, research suggests 2 to 3 percent will develop Leukemia.
In particular, there are two types of Leukemias most affecting the DS population.
1. Acute Myeloid Leukemia (AML)
Children with DS are 150 times more likely to develop AML as opposed to children without DS.
With a whopping 500-fold relative risk, Acute Megakaryocytic Leukemia (AMKL) is a particularly prevalent form of AML.
A condition called Transient Abnormal Myelopoiesis (TAM) – or “Pre-Leukemia” – acts as a precursor to AMKL. Around 10% of infants with DS will present with TAM at birth or shortly after. Although called transient, as most cases resolve in a few months, around 20-30% of these go on to develop AMKL.
Research highlights a significant relationship between mutations in the GATA1 gene and developing TAM. This gene encodes for proteins that help immature blood cells become mature blood cells.
While scientists don’t fully understand how these mutations lead to such a marked risk for AMKL, TAM appeared to come before most cases of AMKL, with the majority of TAM cases having a GATA1 gene mutation.
2. Acute Lymphoblastic Leukemia (ALL)
ALL is the most prevalent cancer in children without DS and is even more so in the DS pediatric population. DS children are around 20 times more likely to develop ALL than non-DS children.
Basically, AML contributes much higher relative risk levels, but ALL still accounts for a larger number of cases in those with DS. Due to this, the ratio of ALL to AML cases in DS children is much lower than in the general pediatric population (1.7 vs 6.5).
Chemotherapy
Curiously, children with DS and AML have very high cure rates when compared to non-DS children. The reason for this could be how AML cells show greater sensitivity to chemotherapy agents such as cytarabine.
On the other hand, ALL does not seem to react the same way to chemotherapy. This, along with higher rates of relapse and developing chemotherapy-related infections, are all added challenges for those with DS and ALL.
Mutual Benefit
Research has yet to fully understand the unique challenges those with DS face when given a cancer diagnosis of any kind.
Research into Down syndrome’s genetic makeup could lead to new cancer treatments that also help the general public. The discovery of the DSRC1 gene, which slows tumor growth, shows that studying DS more has the potential to benefit everyone in the fight against cancer.
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