Hairy Cell Leukemia

What is hairy cell leukemia?

Hairy cell leukemia is a rare, slow-growing cancer of the blood and bone marrow. It starts in a type of white blood cell called a B lymphocyte (B cell), which normally helps the body fight infection. In this condition, abnormal B cells build up in the bone marrow (the spongy tissue inside bones where blood cells are made), in the spleen (an organ in the upper left abdomen that filters blood), and in the bloodstream. Under a microscope, these abnormal cells have fine, hair-like projections on their surface, which is where the name comes from.

Because the abnormal cells crowd the bone marrow, the body often struggles to make enough healthy red blood cells, white blood cells, and platelets. This shortage, rather than the cancer cells themselves, causes most of the problems people notice.

Hairy cell leukemia is classified as a chronic leukemia, meaning it usually develops slowly over months or years rather than weeks. It most often affects middle-aged and older adults and is considerably more common in men than in women. It is uncommon in younger adults and very rare in children. In hospital settings, including at Acibadem, this condition is diagnosed and managed by the Hematology Department, which specializes in blood disorders.

Doctors recognize two main forms: classic hairy cell leukemia, which accounts for the large majority of cases, and a less common form often called hairy cell leukemia variant. The variant form behaves somewhat differently and may respond less predictably to standard treatment, so distinguishing between the two matters for planning care.

Hairy cell leukemia symptoms

Hairy cell leukemia symptoms are often vague at first, and some people have no symptoms at all when the condition is found during a routine blood test. When symptoms do appear, they usually relate to low blood counts or an enlarged spleen. Common symptoms include:

• Persistent tiredness or weakness, often caused by anemia (a low red blood cell count).
• Frequent or unusually severe infections, because of a shortage of healthy infection-fighting white blood cells.
• Easy bruising or bleeding, such as nosebleeds or bleeding gums, linked to low platelets (the cells that help blood clot).
• A feeling of fullness or discomfort in the upper left abdomen, or feeling full after eating only a small amount, caused by an enlarged spleen.
• Unintended weight loss.
• Fever, night sweats, or chills that are not explained by an obvious infection.
• Shortness of breath during ordinary activity, often related to anemia.
• Pale skin.
• Swollen lymph nodes, although this is less common than in some other leukemias.

Symptoms tend to develop gradually. In the early phase, many people feel only mildly more tired than usual. As the bone marrow becomes more crowded, infections may become more frequent and the spleen may grow large enough to be felt below the ribs. In the variant form, the white blood cell count is often high rather than low, and the spleen may be very enlarged, while some of the other features of classic disease may be absent.

Because these symptoms overlap with many other, far more common conditions, having them does not mean you have hairy cell leukemia. Only laboratory testing can confirm the diagnosis.

Causes and risk factors

The exact cause of hairy cell leukemia is not fully understood. Like other cancers, it develops when genetic changes (mutations) inside a cell alter the instructions that control how the cell grows and dies. In classic hairy cell leukemia, researchers have found that nearly all cases share a specific change in a gene called BRAF, known as the BRAF V600E mutation. This change causes the abnormal B cells to keep dividing and to survive longer than they should. The mutation is acquired during a person’s lifetime; it is not inherited from parents and is not passed on to children.

Hairy cell leukemia is not contagious, and it is not caused by anything a person did or did not do. A number of factors appear to be associated with a somewhat higher chance of developing it, though none of them is a proven direct cause:

• Age: most people are diagnosed in middle age or later.
• Male sex: men are diagnosed far more often than women.
• Exposure to certain chemicals: some studies have suggested a link with pesticides, herbicides, or industrial solvents, although the evidence is not conclusive.
• Radiation exposure: as with several blood cancers, prior significant radiation exposure has been suggested as a possible factor.
• Family history: a small number of families have more than one affected member, which suggests that inherited factors may play a minor role in rare cases.

Most people with hairy cell leukemia have none of these exposures, and most people with these exposures never develop the disease.

Diagnosis

Hairy cell leukemia is often first suspected when a routine blood test shows unexpectedly low blood counts. Confirming the diagnosis usually involves several steps.

• Complete blood count (CBC): this test measures the numbers of red cells, white cells, and platelets. In classic hairy cell leukemia, all three are often low, a pattern doctors call pancytopenia. A particular type of white cell called a monocyte is frequently very low, which is a useful clue.
• Peripheral blood smear: a drop of blood is examined under a microscope. The characteristic hairy cells may be seen, although they are sometimes few in number.
• Bone marrow aspiration and biopsy: a small sample of bone marrow is taken, usually from the back of the hip bone, under local anesthetic. This is the key test. In hairy cell leukemia the marrow is often fibrotic (scarred), which can make it hard to draw out liquid marrow, a finding known as a “dry tap.” The solid biopsy sample shows the pattern and extent of abnormal cells.
• Flow cytometry: a laboratory technique that identifies proteins on the surface of cells. Hairy cells carry a distinctive combination of markers, and this test helps separate classic disease from the variant form and from other B-cell cancers that can look similar.
• Immunohistochemistry: special stains applied to the biopsy sample to detect proteins typical of hairy cells.
• Genetic testing: checking for the BRAF V600E mutation supports a diagnosis of classic hairy cell leukemia. The variant form generally does not carry this mutation.
• Imaging: an ultrasound or CT scan of the abdomen may be used to measure the spleen and liver and to look for enlarged lymph nodes. Imaging is not required to make the diagnosis but helps assess how the disease is affecting the body.

Unlike many cancers, hairy cell leukemia does not have a formal numbered staging system. Instead, doctors assess how low the blood counts are, how large the spleen is, and whether symptoms are present, and they use this picture to decide whether treatment is needed now or can safely be deferred.

Hairy cell leukemia treatment options

Hairy cell leukemia treatment has changed considerably over recent decades, and the condition is now considered highly treatable in most cases. The right approach depends on blood counts, symptoms, overall health, and whether the disease is newly diagnosed or has returned. Your hematologist (a doctor specializing in blood disorders) will discuss which option fits your situation.

Observation (watch and wait)

Because hairy cell leukemia grows slowly, treatment is not always needed right away. If blood counts are only mildly low, the spleen is not causing problems, and there are no troublesome symptoms or infections, doctors often recommend regular monitoring with blood tests and check-ups instead of immediate therapy. Treatment is usually started when counts fall to a level that raises the risk of infection, bleeding, or serious anemia, or when symptoms interfere with daily life.

Purine analog chemotherapy

The standard first treatment for most people is a type of chemotherapy called a purine analog. The two drugs used are cladribine and pentostatin. These medicines are given into a vein or, for cladribine, sometimes by injection under the skin. Compared with many chemotherapy regimens, treatment is relatively short: cladribine is often given as a single course over about a week, while pentostatin is given every other week for several months. In many cases a single course produces a complete remission, meaning no disease can be detected by standard tests, and remissions often last for years.

The main side effects are a temporary further drop in blood counts and an increased risk of infection in the weeks after treatment, while the marrow recovers. Fever during this time needs prompt medical assessment. Doctors sometimes prescribe preventive medicines against certain infections during this period.

Immunotherapy with rituximab

Rituximab is an antibody medicine that attaches to a protein on B cells and helps the immune system destroy them. It may be combined with a purine analog, either at the same time or shortly afterward, with the aim of deepening the response and lengthening remission. It is also used on its own or in combinations when the disease returns.

Targeted therapy

For disease that has returned or has not responded to standard chemotherapy, targeted medicines that block the effect of the BRAF mutation, such as vemurafenib, may be used, often together with rituximab. These are taken by mouth. Other targeted drugs are being studied in clinical trials, and your doctor may discuss trial participation if standard options are exhausted.

Other approaches

Interferon alfa, an older immune-stimulating medicine, is now used only occasionally, for example when other treatments are unsuitable. Splenectomy (surgical removal of the spleen) was once a common treatment but is now rarely performed, reserved mainly for situations where the spleen is causing severe problems that do not respond to medication. Blood transfusions, antibiotics, and growth factors that stimulate white cell production may be used as supportive care during periods of very low counts.

After treatment

After a successful course of treatment, follow-up usually consists of periodic blood tests and clinical review. There is no formal rehabilitation program, but regaining energy after chemotherapy can take several months, and gradual return to normal activity is generally encouraged as counts recover.

Living with hairy cell leukemia and outlook

Hairy cell leukemia prognosis is generally considered favorable compared with many other leukemias. Since purine analogs became standard, most people respond well to initial treatment, and long remissions lasting many years are common. Many people go on to live a normal or near-normal life span, and a proportion never need a second course of treatment. It is important to understand, however, that hairy cell leukemia is usually regarded as controllable rather than curable in the strict sense; the disease can return, sometimes a decade or more after treatment, and it can generally be treated again when it does.

Outlook is more guarded for the variant form, which tends to respond less well to purine analogs alone and more often requires combination approaches. Age, other medical conditions, and how the disease responds to the first treatment also influence the long-term picture. Your doctor can give you a more individualized sense of what to expect, though no one can predict the course with certainty.

Day to day, the most important practical issue is infection risk, both from the disease and from its treatment. Simple measures such as careful hand hygiene, avoiding people with obvious infections during periods of low counts, and keeping vaccinations up to date as advised by your care team are commonly recommended. Live vaccines are usually avoided during and shortly after treatment, so vaccination decisions should be made with your hematologist. Balanced nutrition, regular gentle exercise as energy allows, and adequate rest can help with fatigue. Because the condition can be a source of ongoing anxiety, some people find support groups or counseling helpful.

Keeping all follow-up appointments matters even when you feel well, because a gradual fall in blood counts is often the first sign of a relapse and can be picked up before symptoms appear.

Frequently asked questions

What are the first hairy cell leukemia symptoms people usually notice?

The earliest sign is often unexplained tiredness that does not improve with rest. Some people notice they are catching infections more often or that infections take longer to clear, while others notice bruising easily or a feeling of fullness under the left ribs. Quite often there are no symptoms at all and the condition is found on a routine blood test. These symptoms are common to many conditions, so a medical evaluation is needed to find the cause.

Is hairy cell leukemia curable?

Most specialists describe hairy cell leukemia as highly treatable and controllable rather than reliably curable. Treatment frequently produces complete remissions that last for many years, and some people never relapse. Because the disease can come back after long intervals, lifelong follow-up is generally recommended, and repeat treatment is usually effective if relapse occurs.

What is the usual hairy cell leukemia treatment?

When treatment is needed, the standard first option is a purine analog chemotherapy drug, either cladribine or pentostatin, sometimes combined with the antibody medicine rituximab. If the disease returns or does not respond, options may include repeating the purine analog, rituximab-based combinations, or targeted drugs that act on the BRAF mutation. Not everyone needs treatment immediately; mild disease is often monitored first.

What is the hairy cell leukemia prognosis if it is left untreated?

Without treatment, blood counts tend to fall gradually, raising the risk of serious infections, bleeding, and severe anemia, and the spleen may continue to enlarge. However, because the disease is slow-growing, doctors often safely defer treatment in people with mild disease and no symptoms, monitoring them closely and beginning therapy when counts or symptoms indicate it is needed. Delaying treatment under medical supervision is different from leaving the disease untreated.

Is hairy cell leukemia hereditary?

In the great majority of cases, no. The BRAF mutation that drives classic hairy cell leukemia arises in a single cell during a person’s lifetime and is not passed to children. A very small number of families with more than one affected member have been described, suggesting inherited factors may occasionally contribute, but routine genetic testing of relatives is not generally recommended.

How is hairy cell leukemia different from chronic lymphocytic leukemia?

Both are slow-growing B-cell cancers that affect adults, but they differ in important ways. Hairy cell leukemia usually causes low white blood cell counts and a large spleen with few enlarged lymph nodes, while chronic lymphocytic leukemia typically causes a high white cell count and often enlarged lymph nodes. The cells look different under the microscope and carry different surface markers, and the treatments used are not the same, which is why precise diagnosis matters.

Can I work and travel during treatment?

Many people continue working, sometimes with adjustments, particularly since treatment courses are relatively short. In the weeks after chemotherapy, when counts are lowest, your doctor may advise avoiding crowded settings and travel to areas where medical care is limited. Decisions about work and travel are best made individually with your care team based on your counts and how you feel.

When to see a doctor

If you have ongoing tiredness, repeated infections, easy bruising, or discomfort under your left ribs that lasts more than a few weeks, it is sensible to arrange a medical review. A simple blood test can identify low counts and point toward the need for further investigation. If you have already been diagnosed with hairy cell leukemia, whether you are under observation or have completed treatment, certain warning signs need urgent attention, especially during or shortly after chemotherapy when your infection defenses are low. Seek urgent medical care if you experience:

• Fever (a temperature of 38°C / 100.4°F or higher), chills, or shaking, even if you otherwise feel reasonably well.
• Signs of serious infection such as a productive cough with breathlessness, burning on urination, or a red, hot, swollen area of skin.
• Bleeding that will not stop, blood in urine or stool, black stools, or many new unexplained bruises or tiny red spots on the skin.
• Sudden severe pain in the upper left abdomen or pain spreading to the left shoulder, which could indicate a problem with an enlarged spleen.
• Severe shortness of breath, chest pain, or a racing heartbeat.
• Confusion, severe drowsiness, or fainting.
• Persistent vomiting or inability to keep fluids down.

These symptoms can escalate quickly in someone with low blood counts, and early treatment substantially reduces the risk of complications. If you are unsure whether a symptom is serious, it is safer to seek medical advice promptly than to wait.