Leukemia is a cancer of the blood and bone marrow, the spongy tissue inside your bones where blood cells are made. It occurs when the body produces abnormal white blood cells that don’t function properly and crowd out healthy blood cells. Globally, about 460,000 people are diagnosed with leukemia each year, and the overall five-year survival rate in the United States is 67%.
How Leukemia Develops
Your bone marrow constantly produces new blood cells: red blood cells that carry oxygen, white blood cells that fight infection, and platelets that help your blood clot. In leukemia, something goes wrong in the DNA of developing blood cells, causing them to grow and divide uncontrollably. These abnormal cells accumulate in the bone marrow, physically crowding out the production of normal cells.
This crowding effect is what drives most of the symptoms. With fewer healthy red blood cells, you become anemic and fatigued. With fewer platelets, you bruise and bleed easily. And even though your body is overproducing white blood cells, those cells are defective, leaving you vulnerable to infections your immune system would normally handle without trouble.
The Four Major Types
Leukemia is classified along two axes: how fast it progresses (acute or chronic) and which type of white blood cell is affected (lymphoid or myeloid). This creates four main types, each with a distinct profile.
Acute Lymphocytic Leukemia (ALL)
ALL involves immature lymphoid cells and progresses rapidly. It is the most common childhood cancer, though it also occurs in adults. The five-year survival rate is about 72%, with significantly higher rates in children. Because the abnormal cells are immature and multiply quickly, symptoms can appear over days to weeks.
Acute Myeloid Leukemia (AML)
AML affects immature myeloid cells and is more common in older adults. It tends to be the most aggressive form, with a five-year survival rate of roughly 32%. Like ALL, it comes on fast, and bone marrow samples typically show more than 20% immature cells, called blasts.
Chronic Lymphocytic Leukemia (CLL)
CLL involves more mature lymphoid cells and progresses slowly, sometimes over years. Many people are diagnosed through a routine blood test before they ever have symptoms. It carries the highest five-year survival rate of the four types at about 88.5%, and some patients never need treatment, instead following a “watch and wait” approach with their care team.
Chronic Myeloid Leukemia (CML)
CML affects partially mature myeloid cells and typically progresses through a slow, stable phase before potentially accelerating. Its five-year survival rate is around 70%. CML is strongly associated with a specific genetic abnormality called the Philadelphia chromosome, which has made it one of the great success stories of targeted cancer therapy.
Common Signs and Symptoms
Leukemia symptoms vary by type, but many overlap because they stem from the same underlying problem: not enough healthy blood cells. Common signs include persistent fatigue and weakness, fever or chills, frequent or severe infections, and unexplained weight loss.
Because platelets are affected, you may notice easy bruising, recurrent nosebleeds, or tiny red spots on the skin called petechiae. Swollen lymph nodes, an enlarged spleen or liver, excessive night sweats, and bone pain or tenderness are also reported. Acute forms tend to produce symptoms quickly and noticeably, while chronic forms may cause vague, slowly worsening fatigue that’s easy to dismiss for months.
Risk Factors
Most people diagnosed with leukemia have no obvious risk factor, but several exposures are well established. Benzene, a chemical found in gasoline, industrial solvents, and cigarette smoke, is one of the strongest known environmental triggers. The International Agency for Research on Cancer classifies benzene as directly carcinogenic to bone marrow. People with five or more years of occupational benzene exposure have roughly double the risk of developing myeloid leukemias compared to unexposed individuals.
Previous cancer treatment is another significant risk. Certain chemotherapy drugs, particularly a class called alkylating agents, and radiation therapy can damage bone marrow DNA in ways that lead to leukemia years later. Other established risk factors include increasing age, male sex, smoking, obesity, and certain inherited genetic conditions like Down syndrome. Having a family member with leukemia modestly increases risk, though most cases are not inherited.
How Leukemia Is Diagnosed
Diagnosis usually starts with a routine or diagnostic blood test showing abnormal white blood cell counts. A complete blood count may reveal very high or very low white blood cell numbers, along with low red blood cell or platelet counts. But a blood test alone is not enough to confirm leukemia or identify its type.
A bone marrow biopsy, where a small sample is drawn from the hip bone, provides a direct look at the cells being produced. In acute leukemia, more than 20% of the cells in the marrow are immature blasts. Chronic leukemia shows fewer blasts with more partially developed cells.
A technology called flow cytometry plays a central role in pinpointing the exact type. It works by passing individual cells through a laser beam and measuring multiple characteristics of each cell simultaneously, including size, complexity, and which proteins sit on the cell surface. This allows the lab to rapidly sort through thousands of cells, identify the abnormal population, and classify the leukemia into a specific subtype. Additional genetic testing can identify chromosomal abnormalities, like the Philadelphia chromosome in CML, that influence treatment decisions and prognosis.
Treatment Approaches
Treatment depends heavily on the type of leukemia, how far it has progressed, and the patient’s age and overall health. The main categories are chemotherapy, targeted therapy, immunotherapy, and stem cell transplant.
Chemotherapy remains a cornerstone for acute leukemias, typically given in intensive rounds aimed at wiping out the abnormal cells and allowing healthy marrow to recover. For some patients, a stem cell transplant follows, replacing damaged marrow with healthy donor cells. This is a significant procedure with a long recovery, but it offers the best chance of cure for certain high-risk cases.
Targeted therapies have transformed outcomes for specific subtypes. CML is the clearest example: drugs called tyrosine kinase inhibitors block the protein produced by the Philadelphia chromosome, and most patients achieve long-term remission while taking a daily pill. These same drugs also help patients with a specific genetic subtype of ALL.
A newer approach called CAR T-cell therapy has shown strong results, particularly in a form of ALL that affects B cells. In this treatment, a patient’s own immune cells are removed, genetically reprogrammed to recognize leukemia cells, and infused back into the body. For chronic lymphocytic leukemia, combining targeted drugs with CAR T-cell therapy has produced higher remission rates and longer periods without disease progression than either treatment alone.
It’s worth noting that the most recent national survival statistics come from patients diagnosed between 2017 and 2021, meaning they don’t fully reflect improvements from the newest therapies now available. For many patients diagnosed today, outcomes are likely better than those headline numbers suggest.
Acute vs. Chronic: What the Difference Means
The distinction between acute and chronic leukemia is not just about speed. It reflects fundamental differences in the biology of the disease. In acute leukemia, the cancerous cells are immature and poorly differentiated, meaning they never developed into functioning white blood cells. They multiply fast and accumulate rapidly, which is why symptoms can escalate within weeks. Without treatment, acute leukemia is life-threatening in a short timeframe.
Chronic leukemia cells are partially mature. They retain some function and accumulate more slowly, which is why people with chronic forms can go months or even years feeling relatively well. CLL in particular may require no treatment at diagnosis. The tradeoff is that chronic leukemias, while slower, can be harder to cure outright. Many patients manage them as long-term conditions rather than achieving a definitive cure.