Infantile ALL occurs in children under age one. It’s a rare and aggressive leukemia that typically has a poor outlook. Treatment involves chemo and sometimes a stem cell transplant.

Leukemia refers to a group of cancers that start in blood cells in the bone marrow. These cancers are classified based on how fast they grow and which type of blood cells they affect.

Acute lymphoblastic leukemia (ALL) is a type of leukemia that grows quickly. It affects cells that go on to become white blood cells called lymphocytes.

While ALL is most common in early childhood, it’s quite rare in infants. Infantile ALL also tends to be more aggressive and difficult to treat.

Below, we’ll explore more about infantile ALL. We’ll cover topics like symptoms, diagnosis, treatment, and outlook.

Infantile ALL is a type of fast-growing leukemia. It develops in early forms of white blood cells called lymphocytes.

Lymphocytes are infection-fighting immune cells like B cells and T cells. Most diagnoses of infantile ALL affect early forms of B cells.

A leukemia is classified as “infantile” when it’s diagnosed before a child’s first birthday.

Infantile ALL is rare, making up only 2% to 5% of all pediatric diagnoses of ALL. In fact, the Leukemia & Lymphoma Society notes that only about 90 diagnoses of ALL are made in infants in the United States each year.

When the number of leukemia cells builds up in the bone marrow, they begin to crowd out healthy blood cells, including other white blood cells, red blood cells, and platelets.

As these healthy blood cells are crowded out, their numbers start to drop. This is what leads to many of the symptoms of ALL:

  • low red blood cell counts lead to anemia, which can cause symptoms like:
    • extreme tiredness
    • weakness
    • shortness of breath
    • dizziness or lightheadedness
    • pale skin
  • low white blood cell counts can cause persistent fevers and also increase the risk of infections
  • low platelet counts lead to:
    • easy bruising or bleeding
    • frequent bleeding events like nosebleeds and bleeding gums
    • petechiae, small reddish or purplish spots under the skin caused by bleeding

Additional signs and symptoms of infantile ALL can include:

Infantile ALL typically has more aggressive signs and symptoms, including:

  • high numbers of leukemia cells at diagnosis
  • early spread to the CNS, which includes the brain and spinal cord
  • enlarged spleen and liver
  • leukemia cutis, a condition that occurs when leukemia cells spread into the skin

On a basic level, infantile ALL occurs due to genetic changes in early white blood cells. These changes cause these cells to grow and divide uncontrollably.

It’s believed that the genetic changes that cause infantile ALL happen while still in the womb. Research has supported this, finding that the proportion of childhood leukemias, especially infantile leukemias, is higher in twins.

Researchers have identified some genetic changes that happen in infantile ALL. One of these called a KMT2A rearrangement, is found in up to 80% of infants with ALL. It’s associated with resistance to treatment and higher relapse rates.

After learning a child’s medical history and doing a physical examination, a healthcare professional can do additional tests to diagnose infantile ALL.

A complete blood count measures levels of different blood cells. Infants with ALL typically have high white blood cell counts, although most of these are leukemia cells and not mature white blood cells. They can also have low levels of red blood cells and platelets.

A bone marrow aspiration and biopsy collect samples from the bone marrow. These can then be examined under a microscope to look for leukemia cells.

If leukemia cells are found, a healthcare professional can do additional tests on the sample. This can help them to determine the type of cells affected and any genetic changes they may have.

Because infantile ALL often spreads to the CNS, a cerebrospinal fluid (CSF) analysis, which involves a lumbar puncture, may also be done to check for signs of leukemia cells.

Lastly, imaging may be used to look for signs of leukemia outside of the bone marrow. Imaging tests that may be used include things like CT scans, MRI scans, or chest X-rays.

The treatment of infantile ALL differs from how ALL is treated in older children. Due to the fact that ALL in infants tends to be aggressive, more intensive treatment often needs to be used.

The National Comprehensive Cancer Network (NCCN) recommends all infants with ALL be treated as part of a clinical trial, if possible.

There are three phases to the treatment of infantile ALL, and they all have different goals:

  • Induction phase: The induction phase aims to achieve remission, in which blood cell counts and bone marrow samples return to normal.
  • Consolidation phase: During the consolidation phase, additional treatment is given to kill any remaining leukemia cells in the body.
  • Maintenance phase: If ALL is still in remission after the first two phases, the maintenance phase aims to keep the leukemia in remission.

The induction phase of infantile ALL treatment typically involves the use of chemotherapy (chemo), specifically drugs used during the Interfant clinical trials. The drugs include:

Treatment during the induction and maintenance phases depends on a child’s risk group. A healthcare provider will determine risk groups based on:

  • the presence of the KMT2A rearrangement
  • age
  • white blood cell count
  • whether there is minimal residual disease after the consolidation phase

Treatment typically involves chemo, with intensity varying based on the risk group. In some situations, a stem cell transplant may be recommended.

Additional treatment may also be done to address or prevent the spread of leukemia to the CNS. This can involve radiation therapy or chemo given into the bloodstream or CSF.

The outlook for infantile ALL is poor. According to a 2024 review, not only is infantile ALL more aggressive, but it’s also associated with resistance to some types of chemo, high rates of relapse, and treatment-related toxicity.

A 2019 clinical trial reported the 6-year overall survival rates for a group of children with infantile ALL. These percentages represent the percentage of children with infantile ALL that were alive six years after their diagnosis.

  • 58.2% overall
  • 87.2% for infants in the low risk group
  • 58.1% for infants in the intermediate-risk group
  • 29.9% for infants in the high risk group

Some new treatment advances are occurring. For instance, clinical trial results published in 2023 found that adding the targeted therapy drug blinatumomab (Blincyto) to Interfant chemo boosted treatment effectiveness when compared to previous data using just Interfant chemo alone.

Infantile ALL is a rare, aggressive type of leukemia that affects children under the age of one. It’s believed to occur due to genetic changes that happen in the womb.

The treatment for infantile ALL is more intense than the treatment used for other children with ALL. It typically involves the use of chemo. Sometimes a stem cell transplant is recommended.

The outlook for infantile ALL is generally poor but can depend on a child’s risk group. Be sure to see your child’s pediatrician if they develop symptoms like fatigue, shortness of breath, persistent fever, or easy bleeding.