Leukemia is a type of cancer that originates in the blood-forming cells within the bone marrow, the soft, spongy tissue inside bones. This disease involves the rapid and uncontrolled growth of abnormal blood cells, usually immature white blood cells, which can then crowd out healthy blood cells. MLL leukemia is a distinct and aggressive subtype. It is characterized by a unique genetic alteration involving the Mixed-Lineage Leukemia (MLL) gene.
Understanding MLL Leukemia
MLL leukemia is characterized by rearrangements of the MLL gene, also known as KMT2A, located on chromosome 11q23. This gene functions as a transcriptional regulator, playing a role in the development of blood cells and embryonic growth. When the MLL gene undergoes a rearrangement, such as a translocation where a piece of one chromosome breaks off and attaches to another, it fuses with other partner genes.
These rearrangements create abnormal “fusion” proteins. These fusion proteins disrupt the normal regulatory functions of the MLL gene, leading to uncontrolled cell growth and leukemia development. The MLL gene can fuse with over 80 different partner genes, though a small number of these partners account for the majority of MLL-rearranged leukemias. This type of genetic alteration can occur in both acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), with a notable prevalence in infants, accounting for 70% to 80% of acute leukemias in those under one year old.
Recognizing MLL Leukemia
MLL leukemia often presents with general symptoms common to many forms of leukemia. These include persistent fatigue, unexplained fevers, easy bruising or bleeding, and swollen lymph nodes. These non-specific signs often prompt a healthcare provider visit.
The diagnostic process typically starts with a complete blood count (CBC), which can reveal abnormalities in the number of white blood cells, red blood cells, or platelets. If the CBC results suggest leukemia, a bone marrow biopsy is performed. This procedure involves taking a small sample of bone marrow for microscopic examination to confirm the presence of leukemia cells. Specific genetic testing, such as fluorescence in situ hybridization (FISH), polymerase chain reaction (PCR), or next-generation sequencing, is then used to identify the MLL gene rearrangement. This genetic confirmation is important for precisely diagnosing MLL leukemia and distinguishing it from other leukemia subtypes.
Treatment Options for MLL Leukemia
Treatment for MLL leukemia is intensive, primarily involving chemotherapy. The specific chemotherapy protocol often depends on whether the patient has MLL-rearranged ALL or AML, and their age, with distinct protocols for infants. These regimens aim to eliminate the leukemia cells and induce remission.
In some cases, targeted therapies may be used with or after chemotherapy. These newer treatments focus on specific molecular pathways that are disrupted by the MLL fusion proteins. For certain patients, hematopoietic stem cell transplantation, often referred to as a bone marrow transplant, may be considered. This procedure involves replacing the patient’s diseased bone marrow with healthy stem cells, either from a donor or, in some cases, the patient’s own previously collected cells. The decision to pursue transplantation is based on various factors, including the patient’s overall health and the specific characteristics of their leukemia.
Living with MLL Leukemia and Outlook
The outlook for individuals with MLL leukemia can vary, influenced by several factors. These include the patient’s age at diagnosis, the specific MLL fusion partner involved, and how well the leukemia responds to the initial treatment. MLL-rearranged leukemias are often aggressive and can carry a less favorable prognosis.
Long-term follow-up care is important for individuals who achieve remission. This includes ongoing monitoring for any signs of relapse and providing supportive care to manage potential late effects of treatment. Clinical trials also play a role in improving outcomes for patients with MLL leukemia. These trials investigate new therapies and combinations, offering access to innovative treatments and contributing to advancements in understanding and managing this complex disease.