Hairy Cell Leukaemia

Hairy cell leukaemia or HCL is a rare type of blood and bone marrow cancer, which affects your B lymphocytes or the white blood cells that form antibodies to fight off the infections. In HCL, your body produces an excess of B lymphocytes (which have a hairy appearance under the microscope)that do not function normally. These cells use up the space meant for the healthy B lymphocytes, thereby weakening your immune system and making you prone to several infections.

Associated Anatomy

Blood and bone marrow

Alternate Names

In old publications, Hairy cell leukaemia (HCL) was also described as malignant reticulosis, histiocytic leukaemia, or lymphoid myelofibrosis.

Signs and Symptoms of Hairy Cell Leukaemia

You may not necessarily have symptoms with HCL; however, some symptoms associated with later stages of the disease include:

• Persistent fatigue
• Weakness
• Unexplained weight loss
• Shortness of breath
• Excessive sweating, especially at night
• Swollen lymph nodes
• Bone pain, particularly under the ribs
• Frequent infections
• Frequent fever
• Small red spots on the skin
• An enlarged spleen or liver
• Easy bruising and bleeding

Causes of Hairy Cell Leukaemia

• Although the causes of hairy cell leukaemia are unclear, the most likely cause can be attributed to changes or mutations in the DNA.
• These mutations cause excess production of white blood cells (the B lymphocytes) from the stem cells in your bone marrow.
• Consequently, fewer blood stem cells develop into other types of healthy white blood cells, red blood cells, or platelets.
• These abnormal B-lymphocytes do not function properly, can't fight infections, and use up the space of other healthy blood cells.

Possible Treatment For Hairy Cell Leukaemia

Depending on how your HCL is progressing or impacting your life, the doctor may decide any one of the following treatments:

• If your HCL progresses slowly and doesn't show any symptoms, your doctor might resort to "watchful waiting" before starting any actual treatment.
• Chemotherapy: A combination of potent drugs like cladribine (Leustatin) and pentostatin (Nipent) are put into your body through IV. These drugs can kill the cancer cells or at least slow their growth.
• Immunotherapy: Some medicines like rituximab (Rituxan) or interferons enhance your immune system and can be used to fight HCL.
• Surgery: If your spleen bursts or causes severe pain, you may have to undergo a procedure called splenectomy to remove the organ. This procedure may help you get your white blood cells to count back to normal.

Various Stages of Hairy Cell Leukaemia

The stage of cancer implies how far it has progressed. However, there is no widely acknowledged staging system for hairy cell leukaemia.

Typical tests for diagnosing HCL

HCL can be diagnosed in several ways:

• Enlarged lymph nodes or an enlarged spleen can be felt by physically examining the patient.
• Low levels of red blood cells, white blood cells, and platelets in a blood test.
• A bone marrow biopsy can be conducted to check for HCL cells.
• A Computerised tomography or CT scan can be conducted to detect spleen or lymph node enlargement.

Prevention of Hairy Cell Leukaemia

Prevention of HCL is a topic of ongoing research. However, you can try to prevent this condition by avoiding exposure to chemicals, especially those used in farming, and other radiations like x-rays.

Additional Types

Hairy cell leukaemia is a rare and slow-progressing subtype of chronic lymphocytic leukaemia (CLL).

There are two variants of HCL:

• Hairy cell leukaemia variant, HCL-V, is a prolymphocytic variant of HCL. This variant is a rare condition that accounts for nearly 0.4% of chronic lymphoid malignancies and almost 10% of all HCL cases.
• A Japanese variant; which is more difficult to treat.

Differential Diagnosis

The differential diagnosis for HCL includes:

• Hairy cell leukaemia variant (This type of HCL is classically CD25-negative and CD123-negative)
• Splenic marginal zone lymphoma
• Splenic diffuse red pulp lymphoma
• Non-Hodgkin lymphoma

Epidemiology

• Hairy Cell Leukaemia is a rare condition where less than 1 in 10000 people is diagnosed.
• HCL is four to five times more likely to affect men than women.
• The disease usually affects the elderly population, those over 50 years, with an average age of 71 years.

Expected Prognosis

HCL is a chronic condition that may not completely disappear with treatment. Nevertheless, it grows very slowly, and appropriate treatment can help increase life span.

The prognosis of hairy cell leukaemia largely depends on factors like the number of healthy cells present in the blood and bone marrow, an enlarged spleen, the severity of symptoms, and how the HCL responds to treatment.

Hairy cell leukaemia resembles chronic leukaemia when it comes to its prognosis. Often, a timely treatment may result in long-term cures, with a survival rate between 84% to 94%. That being said, sometimes, HCL (especially the refracted or recurred one) may not respond to the treatment or may recur after the treatment.

Your treatment and associated recovery usually depend on the rate at which the abnormal leukaemia cells develop and increase in number. Your symptoms may subside, and the cancer may stop progressing with appropriate treatment. However, you may need to go through the treatment again if your cancer progresses or symptoms return.

Natural Progression

Hairy cell leukaemia usually progresses very slowly and may even remain stable for several years, and that is why it may not show severe complications. However, it may cram the healthy cells in the bone marrow once it progresses, causing further complications like anaemia, various infections, and bleeding.

Pathophysiology

Our bone marrow produces blood stem cells, which eventually mature into myeloid or lymphoid blood stem cells. Myeloid stem cells form red blood cells, white blood cells, or platelets, while lymphoid stem cells grow into B lymphocytes, T lymphocytes, and natural killer cells which form the primary defence system of our body.

In hairy cell leukaemia, an abnormally large number of blood stem cells develop into improper B lymphocytes or leukaemia cells, leaving a tiny room for other healthy blood cells to grow. This results in pancytopenia, which means lowered red blood cells, white blood cells, and platelets, causing further complications.

Risk Factors 

Although the evidence is inconclusive, some factors likely to increase the risk of HCL include:

• Excess exposure to radiation: People who work around x-ray machines and don't wear adequate protective equipment or have received radiation therapy for cancer.
• Excess exposure to chemicals: Some industrial and agricultural chemicals like herbicides may cause HCL.
• Exposure to tobacco smoke and ionising radiation

Possible Complications of Hairy Cell Leukaemia

Untreated hairy cell leukaemia may cause splenomegaly and bone marrow failure, causing complications like:

• Increased frequency of infections (due to the reduced number of healthy white blood cells)
• Bleeding (because of a decreased platelet count)
• Anaemia (because of reduced red blood cell count)
• Lack of oxygen in your body

People with HCL may have an increased risk of secondary malignancies, either through the disease itself or as a side effect of immunosuppressive therapies. That is why they are likely to get skin cancer (melanoma or non-melanoma) which forms about 33 to 36% of secondary malignancies.