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Diagnosis and tests

Symptoms of hairy cell leukemia

The related article (“Hairy cell leukemia: symptoms and diagnosis”) explains how to prepare for a bone marrow test. This topic looks closely at the symptoms of a rare B-cell leukaemia, hairy cell leukaemia.

Last updated: ~1 min read
A lymphocyte with a hairy edge.
Figure 1.A cell with hair-like projections.

01Short answer

Hairy cell leukaemia is a rare, slow-growing B-cell leukaemia, seen more often in middle-aged men. It is named after the fine “hairs” around the edge of the cells under the microscope. The leukaemia cells fill the bone marrow and the spleen. So the main symptoms are tiredness and weakness (anaemia); easy bruising and bleeding (low platelets); repeated or unusual infections, because neutrophils and especially monocytes are very low; and heaviness under the left ribs and feeling full quickly because of an enlarged spleen. Interestingly, lymph nodes are usually not enlarged, and there are few leukaemia cells in the blood. Symptoms build up gradually over months; sometimes the disease is found by chance because of low blood counts.

02Simple explanation

A rare, slow B-cell leukaemia.

A large spleen, low counts.

Few monocytes: infection risk.

03Scientific explanation

Monocytopenia: an almost complete lack of monocytes is typical of hairy cell leukaemia and creates a tendency to unusual infections.

Dry tap: because the marrow is fibrous, aspiration may yield no fluid, so a biopsy is important.

04What happens in the body?

A hairy cell

Fine projections around the cell’s edge gave it its name.

A big spleen, few cells

The spleen grows while blood counts fall.

A body with a large spleen.
Figure 2.A large spleen and low counts.

Few monocytes

A lack of monocytes raises the risk of infection.

A bloodstream with bacteria.
Figure 3.Few monocytes and infection.

05How symptoms appear

Four steps.

Tiredness — Over months.1TirednessOver months.
Spleen — Heaviness on the left.2SpleenHeaviness on the left.
Infection — Unusual.3InfectionUnusual.
Test — Low counts.4TestLow counts.

06Hairy cell leukaemia compared

FeatureHairy cell leukaemia
SpleenOften large
Lymph nodesUsually not enlarged
MonocytesVery few
Leukaemia cells in the bloodFew
CourseSlow

07Key terms

Hairy cell
A B cell with fine projections around its edge.
Pancytopenia
A fall in all blood cells.
Monocytopenia
Too few monocytes.
Splenomegaly
An enlarged spleen.
Dry tap
Aspiration that yields no fluid.

08Key points

  • It is a rare, slow leukaemia.
  • The spleen is often enlarged.
  • Blood counts are low.
  • Monocytes are very few.
  • Infections can be serious.
  • Lymph nodes are usually not enlarged.

09Frequently asked questions

Is it the same as CLL?

No; both are B-cell leukaemias, but they are different diseases (“How hairy cell leukemia is diagnosed”).

Why are infections unusual?

A lack of monocytes weakens defence against some germs.

Does it occur in women?

Yes, but less often.

10Questions for your doctor

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  1. Is it the same as CLL?

  2. Why are infections unusual?

  3. Does it occur in women?

My questions

12Sources

  1. National Cancer Institute (NCI). Hairy cell leukemia treatment (PDQ), patient version
  2. MedlinePlus. Blood smear
  3. MedlinePlus. Bone marrow biopsy
  4. Blood Cancer United (formerly The Leukemia & Lymphoma Society). Chronic myeloid leukemia (CML) signs and symptoms
  5. Blood Cancer United (formerly The Leukemia & Lymphoma Society). Diagnosing CML
  6. NHS. Chronic myeloid leukaemia — Tests and next steps
  7. Annals of Oncology (ESMO), 2017. Chronic myeloid leukaemia: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up
  8. American Journal of Hematology, 2024. Chronic myeloid leukemia: 2025 update on diagnosis, therapy, and monitoring
  9. American Cancer Society. Signs and Symptoms of Chronic Lymphocytic Leukemia
  10. Blood Cancer United (formerly The Leukemia & Lymphoma Society). Chronic lymphocytic leukemia (CLL) signs and symptoms
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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