FLT3-ITD positive acute myeloid leukemia is a type of AML in which the leukemia cells carry an internal tandem duplication (ITD) in the FLT3 gene, a change that keeps a growth-signaling receptor permanently switched on. It is one of the most common mutations in AML, tends to cause high white cell counts and a higher risk of relapse, and is found by molecular testing of blood or bone marrow at diagnosis. Knowing a patient is FLT3-ITD positive matters because it adds a targeted FLT3 inhibitor to treatment and often points toward a stem cell transplant in first remission.
AML is one of the more aggressive hematological disorders, and FLT3 status is now one of the first results a treating team waits for. Here is what it means in plain terms.
What the FLT3-ITD Mutation Does
FLT3 (FMS-like tyrosine kinase 3) is a receptor on the surface of early blood-forming cells. Normally it switches on only when its matching signal molecule (FLT3 ligand) binds, telling young cells to survive and multiply during normal blood production.
An internal tandem duplication is a stretch of the gene that has been copied and inserted back in, usually in the juxtamembrane domain, the part that normally keeps the receptor in an “off” position. With that brake damaged, the receptor signals continuously without needing its ligand. Downstream pathways that drive growth and block cell death, including STAT5, PI3K/AKT, and RAS/MAPK, stay active, and leukemic blasts multiply rapidly.
FLT3 mutations as a group are found in roughly a third of adults with newly diagnosed AML, with ITDs making up the larger share. A second, less common type, the tyrosine kinase domain (TKD) point mutation, also activates the receptor but carries different prognostic weight.
Risk Factors and How It Presents
FLT3-ITD is an acquired mutation that arises in the leukemia cells themselves; it is not inherited and is not passed to children. General AML risk factors, such as older age, prior chemotherapy or radiation, benzene exposure, and earlier hematologic conditions like myelodysplastic syndromes, apply here too, but none specifically causes the ITD.
Symptoms are those of AML generally, arising because leukemic cells crowd out normal production:
- Fatigue and breathlessness from anemia.
- Fevers and repeated infections from a shortage of working neutrophils.
- Easy bruising, nosebleeds, or bleeding gums from low platelets.
- A high white cell count at presentation, which is typical of FLT3-ITD disease and can occasionally cause sluggish blood flow (leukostasis) needing urgent treatment.
Because FLT3-ITD disease can progress quickly, these symptoms warrant same-day assessment rather than a routine appointment.
How FLT3-ITD Is Diagnosed
AML is diagnosed by examining the marrow, the spongy tissue described in our overview of bone marrow composition and function. A bone marrow aspiration and biopsy confirms the diagnosis, and samples are sent for several parallel tests.
| Test | Purpose |
|---|---|
| Morphology (microscope review) | Counts blasts; 20% or more blasts in blood or marrow is the traditional threshold for AML |
| Flow cytometry | Confirms the cells are myeloid and records their surface marker “fingerprint” |
| Cytogenetics / FISH | Looks for chromosome changes that shape risk grouping |
| FLT3 PCR (fragment analysis) | Detects the ITD quickly; results are prioritized so targeted therapy can start during induction |
| Next-generation sequencing panel | Identifies co-mutations such as NPM1, DNMT3A, or TP53 that refine prognosis |
FLT3 testing is urgent. Guidelines recommend having the result within the first few days so that an FLT3 inhibitor can be added to the first cycle of chemotherapy. Testing is repeated at relapse, because the mutation can appear or disappear as the disease evolves.
Prognosis and Risk Stratification
Historically, FLT3-ITD marked a higher chance of relapse after chemotherapy alone, especially when the mutated allele made up a large proportion of the FLT3 gene copies (a high allelic ratio). Current European LeukemiaNet (ELN) risk classification places FLT3-ITD in the intermediate-risk group regardless of allelic ratio, unless other findings move the patient into favorable or adverse categories.
Co-mutations matter. FLT3-ITD often occurs alongside NPM1 mutations, and the combination behaves differently from FLT3-ITD alone. Response to initial treatment, including measurable residual disease (MRD) testing after chemotherapy, is also a strong guide to outlook.
Treatment Options
Induction with an FLT3 inhibitor
For patients fit for intensive therapy, standard induction chemotherapy (“7+3”: cytarabine for seven days plus an anthracycline such as daunorubicin for three) is combined with an oral FLT3 inhibitor. Midostaurin is approved with induction and consolidation for FLT3-mutated AML, and quizartinib is approved in several regions specifically for newly diagnosed FLT3-ITD positive AML.
Stem cell transplant
Many patients with FLT3-ITD positive AML are offered an allogeneic stem cell transplant in first remission, using donor stem cells to replace the marrow and provide an immune attack against residual leukemia. After transplant, maintenance with an FLT3 inhibitor such as sorafenib or gilteritinib may be used to lower relapse risk.
Relapsed disease and less intensive options
Gilteritinib is approved as a single agent for relapsed or refractory FLT3-mutated AML. For older or less fit patients, lower-intensity regimens such as azacitidine with venetoclax are used, sometimes with an FLT3 inhibitor added within clinical trials. Supportive care, including transfusions, infection prevention, and monitoring for differentiation syndrome with some agents, runs alongside all of these.
Key Takeaways
- FLT3-ITD is an acquired mutation that locks a growth receptor in the “on” position and is one of the most common mutations in AML.
- Rapid molecular testing at diagnosis is essential so a FLT3 inhibitor can start with the first cycle of chemotherapy.
- Midostaurin or quizartinib with intensive chemotherapy, followed by transplant for suitable patients, is the backbone of modern treatment.
- Gilteritinib is an effective option at relapse, and MRD testing helps guide decisions after remission.
- Ask your team about clinical trials, which remain an important route to newer combinations. For broader context, see our leukemia hub.
Frequently Asked Questions
Is FLT3-ITD positive AML inherited?
No. The ITD develops in the leukemia cells during a person’s lifetime and is not present in the rest of the body’s cells. It cannot be passed on to children, and family members do not need testing for it.
What is the difference between FLT3-ITD and FLT3-TKD?
Both activate the FLT3 receptor, but ITDs are duplicated segments near the membrane, while TKD mutations are single-letter changes in the kinase domain. ITDs have historically carried more relapse risk, and some FLT3 inhibitors, such as quizartinib, act on ITD but not TKD mutations.
Does everyone with FLT3-ITD AML need a stem cell transplant?
Not always. Transplant is commonly recommended in first remission, but the decision weighs co-mutations, MRD results, age, fitness, and donor availability. Your hematologist will discuss the balance of relapse risk against transplant risk.
How long do FLT3 inhibitors need to be taken?
It depends on the drug and treatment phase. Some are given during specific days of chemotherapy cycles, then continued as maintenance for a set period, while gilteritinib at relapse is taken daily as long as it remains effective and tolerated.
