You may have already heard about allergy risk increasing in a baby or child who was kept too clean during their childhood – the so-called “hygiene hypothesis”. This is thought to be due to the immune system not getting enough of a workout in the early years and consequently it becomes super-sensitized when the kid is older, and reacts to inappropriate triggers.
Now it is looking like it is a similar situation for a certain type of leukemia.
Results from a new study suggest that germ-free childhoods followed by infections later in life can increase the risk of the most common childhood leukemia, acute lymphoblastic leukemia (ALL). This study found that ALL is caused by a two-step process. The first step is a genetic mutation that happens in the womb and which predisposes the baby to developing this type of leukemia. The second step is a hygienic early childhood, with few infections, followed by exposure to particular infections later in childhood.
Specifically, the study suggested that children who grew up in cleaner households during their first year and also interacted less with other children, and got fewer infections from those other children, may be more likely to develop ALL. The lead author, Mel Greaves, believes that when a baby is exposed to infections during its first year, its immune system is strengthened. However, infections that occur later in childhood, without the initial priming during the first year, can trigger leukemia in those with the genetic mutation.
The study was a review of more than 30 years of research on the genetics, cell biology, epidemiology, immunology and animal modeling of childhood leukemia. ALL is most often diagnosed in children aged zero to four years old, although older children and adults can also be diagnosed with it. ALL is an aggressive disease, spreading rapidly throughout the body, and chemotherapy is the main form of treatment.
Rates of the disease are increasing globally, with one study estimating around 53,000 new cases globally in 2016. In the US, around 5,960 new cases are estimated to be diagnosed in 2018 .
Luckily ALL is still quite a rare disease and of the children born with the predisposing mutation, only 1 percent will go on to develop ALL.
Rates of ALL are higher in advanced, affluent societies which suggests the second step might be linked to aspects of modern life. In conclusion, this research suggests that ALL may be preventable; however more studies are needed to confirm these results.
The lead author of the study, Mel Greaves, also debunked other claimed causes of ALL, such as electromagnetic radiation and air pollution.
However, other risks include:
- Being exposed to x-rays before birth.
- Being exposed to radiation.
- Past treatment with chemotherapy.
- Having certain genetic conditions, such as:
- Down syndrome
- Neurofibromatosis type 1
- Bloom syndrome
- Fanconi anemia
- Li-Fraumeni syndrome
- Constitutional mismatch repair deficiency (mutations in certain genes that stop DNA from repairing itself, which leads to the growth of cancers at an early age)
- Having certain changes in the chromosomes or genes
What are the symptoms of acute lymphoblastic leukemia?
These and other signs and symptoms may be caused by childhood ALL or by other conditions. Check with your child’s doctor if your child has any of the following:
- Easy bruising or bleeding
- Petechiae (flat, pinpoint, dark-red spots under the skin caused by bleeding)
- Bone or jointpain
- Painless lumps in the neck, underarm, stomach, or groin
- Pain or feeling of fullness below the ribs
- Weakness, feeling tired, or looking pale
- Loss of appetite