Hairy cell leukaemia is a rare type of blood cancer that develops slowly and gets its unusual name from how the diseased cells look under a microscope. While it’s a serious diagnosis, many people with this condition can lead normal lives with proper monitoring and treatment when needed.

Understanding Hairy Cell Leukaemia

Hairy cell leukaemia is a cancer that affects a specific type of white blood cell known as B lymphocytes, also called B cells. These cells normally help your body fight off infections by producing antibodies. In this condition, the bone marrow produces too many abnormal B cells that don’t work properly. When viewed under a microscope, these diseased cells have thin, hair-like projections sticking out from their surface, which is why doctors named this cancer “hairy cell leukaemia.”^[1]

The abnormal cells don’t die when they should as part of the natural cell life cycle. Instead, they keep living and gradually build up in the bone marrow, which is the soft, spongy tissue inside your bones where blood cells are made. These hairy cells can also accumulate in other parts of your body, particularly the spleen, liver, and lymph nodes. As the abnormal cells multiply, they take up space that should be used for producing healthy blood cells, leading to various health problems.^[3]

This type of leukaemia is quite different from other blood cancers because it usually develops very slowly. Some people may have the condition for months or even years before they notice any symptoms or need treatment. It’s considered a chronic leukaemia, meaning it progresses gradually rather than rapidly.^[4]

How Common Is Hairy Cell Leukaemia?

Hairy cell leukaemia is genuinely rare. It accounts for only about two percent of all adult leukaemias. In the United States, approximately one thousand to twelve hundred new cases are diagnosed each year. To put this in perspective, this means the condition affects roughly three out of every hundred thousand people in Europe and North America.^[2][6]

The disease shows clear patterns in who it affects. Men are much more likely to develop hairy cell leukaemia than women, with men being affected about four times as often. The median age when people receive their diagnosis is around fifty-five years, though it can occur in people between the ages of forty and seventy. It’s extremely rare in children and young adults. The condition is more common among people of white ethnicity and Ashkenazi Jewish ancestry compared to other ethnic groups. It appears less frequently in Asia, Africa, and the Middle East.^[6][8][9]

What Causes Hairy Cell Leukaemia?

Scientists don’t fully understand what causes hairy cell leukaemia. What they do know is that it involves changes that happen to B cells after a person is born. These changes aren’t inherited from parents, but rather occur during a person’s lifetime. The condition starts when B cells undergo specific genetic changes in their DNA, which contains all the instructions cells need to function properly.^[4]

Research has uncovered an important clue about what goes wrong in the cells. About ninety to ninety-five percent of people with hairy cell leukaemia have a specific change in a gene called BRAF, particularly the mutation known as BRAF V600E. The BRAF gene normally helps control how cells grow and divide. When this mutation occurs, it causes cells to multiply rapidly and survive when they should die, eventually becoming cancerous. This discovery has been significant because it helps doctors confirm the diagnosis and understand how the disease works.^[4][6][9]

However, researchers still don’t know exactly what triggers this genetic change to happen in the first place. They’re working to understand why some people develop this mutation while most others never do.

Risk Factors

While the exact cause remains unclear, certain factors appear to increase the likelihood that someone might develop hairy cell leukaemia. Age is one important factor, as the condition most commonly affects middle-aged and older adults, with most diagnoses occurring in people around fifty-eight years old. Being male significantly increases risk compared to being female.^[4]

Exposure to certain chemicals may play a role. Studies have found a connection between exposure to Agent Orange, a herbicide used during the Vietnam War, and later development of hairy cell leukaemia. The United States Institute of Medicine has identified a correlation between herbicide exposure and chronic B-cell leukaemias in general, including hairy cell leukaemia. Exposure to certain pesticides and industrial chemicals has also been studied as possible risk factors.^[8][9]

Some research suggests that certain occupations might carry higher risk. Farming and working with large animals has shown associations with increased rates of hairy cell leukaemia in some studies, though this doesn’t necessarily prove these activities directly cause the disease. Having a family history of hairy cell leukaemia appears to slightly increase risk, though this doesn’t mean the condition is inherited. Rather, family members might share a slightly higher chance of developing the same type of genetic mutation after birth.^[8][9]

Importantly, many common cancer risk factors don’t appear to increase the chance of developing hairy cell leukaemia. Studies haven’t found strong links with tobacco smoking or exposure to ionising radiation. Most people diagnosed with this condition have no identifiable risk factors at all.^[8]

Symptoms and Signs

One of the challenging aspects of hairy cell leukaemia is that it often doesn’t cause symptoms in its early stages. Some people discover they have the condition completely by accident when they have blood tests done for unrelated reasons. When symptoms do appear, they usually develop slowly over time as the abnormal cells build up and interfere with the production of normal blood cells.^[1][4]

Fatigue is one of the most common symptoms people experience. This tiredness happens because the body doesn’t have enough healthy red blood cells to carry oxygen to all the tissues. This condition, called anaemia, can make people feel exhausted even after rest. They might feel weak and struggle to do everyday activities that never used to be difficult. Some people also experience shortness of breath during normal activities because their bodies aren’t getting enough oxygen.^[3][4]

Frequent infections are another major sign. When hairy cell leukaemia reduces the number of healthy white blood cells, the body becomes less able to fight off bacteria, viruses, and other germs. People might find themselves getting sick more often than usual, developing fevers, or taking longer to recover from illnesses that would normally clear up quickly.^[3][9]

Many people with hairy cell leukaemia develop an enlarged spleen, which occurs in more than ninety percent of cases. The spleen is an organ located on the left side of the abdomen, just below the ribcage. When hairy cells accumulate there, the spleen swells and can cause a feeling of fullness or discomfort on the left side. This can make people feel full after eating only small amounts of food because the enlarged spleen presses against the stomach. Some people experience pain or a heavy feeling in that area. Similarly, the liver can become enlarged, causing discomfort on the right side of the abdomen.^[2][4][9]

Easy bruising and bleeding problems can occur because hairy cell leukaemia interferes with the production of platelets, the blood cells that help blood clot. People might notice they bruise more easily than before, have nosebleeds, bleed for longer than normal from cuts, or in women, experience heavier menstrual periods.^[3][4]

Some people develop swollen lymph nodes, which might appear as painless lumps in the neck, underarms, or groin. Weight loss without trying to lose weight can also occur. Unlike some other cancers, people with hairy cell leukaemia rarely experience constitutional symptoms like night sweats, chills, or rigours.^[3][8]

Prevention

Unfortunately, there are no known ways to prevent hairy cell leukaemia. Because scientists don’t fully understand what causes the genetic changes that lead to this condition, and because most people who develop it have no identifiable risk factors, there are no specific lifestyle changes or screening programmes that can prevent it from occurring.^[1]

The genetic mutation that causes hairy cell leukaemia happens after birth and isn’t inherited, so it can’t be prevented through genetic counselling or family planning. Unlike some other cancers where avoiding certain substances or adopting healthy behaviours can reduce risk, hairy cell leukaemia doesn’t have such clear-cut prevention strategies.

However, if you have known risk factors such as occupational exposure to certain chemicals or pesticides, taking appropriate safety precautions at work is sensible. This includes wearing protective equipment and following safety guidelines. If you’re a veteran who was exposed to Agent Orange, being aware of this potential connection might help you and your doctors watch for early signs, though this isn’t prevention in the traditional sense.

Maintaining overall good health through regular exercise, a balanced diet, not smoking, and limiting alcohol consumption is always beneficial for general wellbeing, even though these measures haven’t been specifically linked to preventing hairy cell leukaemia. Regular check-ups with your doctor can help identify health problems early, though routine screening specifically for this rare condition isn’t recommended for the general population.

How the Disease Affects the Body

To understand how hairy cell leukaemia affects the body, it helps to know what normally happens in your bone marrow. In healthy people, the bone marrow constantly produces blood stem cells that mature into three main types of blood cells. Red blood cells carry oxygen throughout the body. White blood cells, including several different types, fight infections. Platelets help blood clot to stop bleeding when you’re injured.^[3]

In hairy cell leukaemia, the bone marrow produces too many abnormal B lymphocytes. These diseased cells don’t function properly and can’t help fight infections the way healthy white blood cells do. More importantly, as these hairy cells accumulate in the bone marrow, they physically crowd out the spaces where healthy blood cells should develop. This crowding effect means the bone marrow produces fewer red blood cells, fewer normal white blood cells, and fewer platelets. This condition, where all three types of blood cells are reduced, is called pancytopenia.^[2][3]

The bone marrow in people with hairy cell leukaemia often becomes fibrotic, meaning it develops scar-like tissue that makes it harder for healthy cells to grow. This fibrosis can make it difficult for doctors to draw samples from the bone marrow during diagnostic procedures.^[2]

The hairy cells don’t just stay in the bone marrow. They spill over into the bloodstream and travel to other organs. They particularly accumulate in the spleen, which is responsible for filtering blood and removing old blood cells. As hairy cells build up there, the spleen enlarges, sometimes becoming several times its normal size. The liver can also become enlarged as hairy cells infiltrate it. In some cases, lymph nodes in the abdomen may be affected, though visible swelling of lymph nodes is less common.^[2][3]

A distinctive feature of hairy cell leukaemia is monocytopenia, which means having very low or absent levels of monocytes, a specific type of white blood cell. This finding often helps doctors distinguish hairy cell leukaemia from other blood disorders. The combination of reduced blood cell counts and impaired immune function makes people vulnerable to infections, which can sometimes be serious or life-threatening if not treated promptly.^[2][3]

The disease can also affect cholesterol levels, with some patients showing somewhat reduced cholesterol, especially when the spleen is very enlarged. In rare cases of recurrent disease, the cancer can affect bones themselves, creating lesions that might be confused with other conditions like multiple myeloma. However, these complications are uncommon.^[8]

Despite these wide-ranging effects on the body, hairy cell leukaemia progresses slowly in most people. The gradual nature of the disease means that the body has time to adapt to some of the changes, which is why many people don’t experience severe symptoms until the condition is quite advanced. With modern treatments, the disease can often be controlled effectively, allowing many organs to return to normal or near-normal function.^[1][8]