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Diagnosis and tests

Symptoms in children

Leukemia is the most common cancer in children and teenagers, but overall it is a rare illness. Children cannot always put what they feel into words: they may limp, not want to play or keep getting ill. This topic calmly explains how leukemia can show up in children and when to see a doctor.

Last updated: ~5 min read
A quiet corner of a child’s room in dark navy tones: untouched toys on a soft rug, a small pillow and blanket beside them, and faint evening light from the window; no people.
Figure 1.A child often shows signs through behaviour rather than words.

01Short answer

According to the ACS, about 3 in 4 leukemias in children and teens are acute lymphoblastic leukemia (ALL); it is most common between the ages of 2 and 5. Most of the rest are AML. In children, as in adults, signs come from a drop in healthy blood cells: pallor, tiredness and irritability (anaemia); easy bruising, petechiae and nose or gum bleeding (few platelets); frequent or lingering infections and fever without a clear cause (few normal white cells). Signs that are especially typical in children include bone and joint pain, limping, refusing to walk and pain that wakes them at night; a swollen tummy (liver and spleen), enlarged glands in the neck, armpits or groin, poor appetite and weight loss. In teenagers, T-ALL can cause a cough, breathlessness or a swollen face because of a mass in the chest. In babies, AML can show up as skin lumps and swollen gums. Many of these signs also occur in ordinary childhood illnesses; a full blood count and a doctor’s examination bring clarity.

02Simple explanation

A child often cannot say “I’m tired”: they simply play less, get cross quickly or sleep a lot.

Leg or back pain, limping and wanting to be carried are possible signs of leukemia in children — but usually the cause is something else.

Bruises in places that were not knocked (tummy, back) and tiny red spots deserve attention.

One sign is usually no cause for worry. Several signs together that do not go away are a reason to see a doctor.

The simplest check is a full blood count.

03Scientific explanation

How common is it? The ACS reports that leukemia is the most common cancer in children and teens, but it is rare overall. About 3 in 4 childhood leukemias are ALL, peaking at ages 2 to 5; AML occurs throughout childhood. The WHO notes that early detection and proper treatment of childhood cancer greatly improve outcomes.

Bone pain. The ACS explains that bone and joint pain arise when leukemia cells build up in the bone marrow or near the surface of the bone. In young children this can look like limping, refusing to walk or waking at night, and it is sometimes mistaken for childhood arthritis or an injury.

Other signs. According to the NCI, in childhood ALL an enlarged liver and spleen can cause a swollen tummy and poor appetite, and lymph nodes may enlarge. In T-ALL, a mass in the thymus can press on the windpipe or the superior vena cava — an emergency. If leukemia affects the CNS, headache, vomiting or seizures can occur. Rarely, boys have painless swelling of a testicle.

When to check? Under the UK’s NICE NG12 guidance, children with unexplained petechiae or an enlarged liver and spleen should be referred immediately for specialist assessment. For pallor, persistent tiredness, unexplained fever or repeated infections, widespread enlarged lymph nodes, persistent bone pain, or unexplained bruising or bleeding, a very urgent full blood count within 48 hours is recommended.

04What happens in the body?

How does a child “say” it?

Instead of saying “I feel unwell”, a young child sleeps more, loses interest in toys and wants to be carried. They may show pain by limping, refusing to climb stairs or crying at night. A school-age child may say they get tired quickly in class or skip sports.

Bone and joint pain

Growing pains usually come in the evening in both legs, are gone by morning, and the child plays normally during the day. Pain that deserves attention stays in one place, wakes the child at night, or comes with limping, swelling, fever or pallor.

A schematic image of translucent child’s leg bones on a dark navy background; a soft warm glow at the knee represents pain; no face.
Figure 2.Bone pain that wakes a child at night and does not go away needs attention.

Skin and bleeding

Bruises on the knees and shins are normal in children. Bruises on the tummy, back or face, tiny red spots that do not fade when pressed, frequent nosebleeds or bleeding when brushing teeth should be shown to a doctor.

In teenagers

Teenagers may hide signs or put them down to stress, sport or schoolwork. T-ALL is more common at this age; a persistent cough, breathlessness when lying down and swelling of the face or neck need urgent checking.

How to record what you notice

Keep a small diary: the sign, when it started, temperature, photos of bruises, appetite and sleep. This helps the doctor see how things are changing. Photos, especially of rashes and bruises, are very useful.

An open notebook on a desk on a dark navy background, with a digital thermometer, a phone and a pen beside it; illegible notes and small calendar marks on the pages.
Figure 3.A parent’s diary helps the doctor see how things change.

05From worry to clarity

Simple steps, calm decisions.

Notice — Write down the signs and dates.1NoticeWrite down the signs and dates.
Doctor — A paediatric examination and questions.2DoctorA paediatric examination and questions.
Blood test — A full blood count and blood film.3Blood testA full blood count and blood film.
Result — Normal means reassurance; changes mean a children’s hematologist.4ResultNormal means reassurance; changes mean a children’s hematologist.
Early clarityThe cause is found quickly.
Together with the familyParents’ observations matter.
Peace of mindMost often the cause is simple.

06Signs in children: ordinary causes and when to take note

SignUsually an ordinary causeSee a doctor if
Leg painGrowing pains, a knock, activityWakes at night, limping, fever, pallor
BruisesPlay knocks on knees and shinsOn the tummy, back or face; with petechiae
TirednessLack of sleep, a viral infectionLasts for weeks, with pallor
FeverViral infectionsNo cause, keeps coming back, lasts long
Enlarged glandsThroat and tooth infectionsFirm, painless, growing, in several areas
Swollen tummyConstipation, windLiver or spleen can be felt

* This table does not replace a doctor’s examination. If you are worried, talk to your child’s doctor.

07Key terms

ALL
Acute lymphoblastic leukemia — the most common leukemia in children.
AML
Acute myeloid leukemia.
Petechiae
Tiny red-purple spots that do not fade when pressed.
Hepatosplenomegaly
An enlarged liver and spleen.
Lymphadenopathy
Enlarged lymph nodes.
Growing pains
Harmless evening leg pains in children.
Mediastinal mass
A growth in the centre of the chest; seen in T-ALL.
Paediatric hematologist
A doctor who treats blood disorders in children.

08Key points

  • Leukemia in children is rare; most cases are ALL.
  • Children show signs through behaviour.
  • Bone pain that wakes at night and limping need attention.
  • Bruises in unusual places and petechiae should be checked.
  • Several signs together are what matters.
  • A full blood count is a simple first step.
  • Parents’ observations are very valuable.

09Frequently asked questions

My child’s blood count is normal. Is leukemia ruled out?

A normal full blood count and blood film make leukemia much less likely. But if signs continue or new ones appear, see the doctor again — sometimes a repeat test is needed.

Is leukemia contagious? Could their sister get it?

Leukemia is not contagious. The risk in brothers and sisters may be slightly higher, but it is still very low. Discuss specific questions with the doctor.

Did I miss something? Could I have noticed sooner?

The signs of childhood leukemia look very like ordinary illnesses and develop quickly. Parents very rarely “notice too late”. Do not blame yourself — what matters is taking the right step now.

Is the risk different for children with Down syndrome?

Yes, children with Down syndrome have a higher risk of leukemia and are usually followed more closely. Discuss this with your child’s doctor.

What should I tell my child?

Speak simply, honestly and in a way that suits their age: “The doctor will look at your blood to find out why you are tired.” Children’s psychologists and nurses can help with this conversation.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. My child’s blood count is normal. Is leukemia ruled out?

  2. Is leukemia contagious? Could their sister get it?

  3. Did I miss something? Could I have noticed sooner?

  4. Is the risk different for children with Down syndrome?

  5. What should I tell my child?

My questions

12Sources

  1. American Cancer Society. Signs and Symptoms of Childhood Leukemia
  2. American Cancer Society. Key Statistics for Childhood Leukemia
  3. American Cancer Society. Tests for Childhood Leukemia
  4. American Cancer Society. How Is Childhood Leukemia Classified?
  5. National Cancer Institute (NCI). Childhood Acute Lymphoblastic Leukemia Treatment (PDQ®) — Patient Version
  6. National Cancer Institute (NCI). Childhood Acute Myeloid Leukemia and Other Myeloid Malignancies Treatment (PDQ®) — Patient Version
  7. National Cancer Institute (NCI). Cancer in Children and Adolescents — Fact Sheet
  8. NHS. Symptoms of acute lymphoblastic leukaemia
  9. National Institute for Health and Care Excellence (NICE). Suspected cancer: recognition and referral (NG12)
  10. Children & Young People’s Cancer Association (CCLG). Leukaemia in children
  11. World Health Organization. Childhood cancer — Fact sheet
  12. NHS. Symptoms of acute myeloid leukaemia
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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