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How is JMML diagnosed?

Juveline myelomonocytic leukaemia is diagnosed by examining samples of your child’s blood and bone marrow.

Full blood count

The first step in the diagnosis is a simple blood test called a full blood count (FBC) or complete blood count (CBC). This involves a sample of blood from a vein in your child’s arm being sent to the laboratory for investigation. Some children with JMML have elevated Haemoglobin F levels for their age.

Many of the white blood cells may be abnormal JMML cells. A JMML diagnosis needs to be confirmed by examining the cells in the bone marrow.

Bone marrow examination

If the results of the blood tests suggest JMML, a bone marrow biopsy may be required to help confirm the diagnosis. A bone marrow biopsy involves taking a sample of bone marrow (usually from the back of the hip bone) and sending it to the laboratory for examination under the microscope.

The bone marrow biopsy may be done in the haematologist’s rooms, clinic or day procedure centre and is usually performed under a light anaesthetic or sedation through a small drip in your child’s arm.

The sample of bone marrow is examined in the laboratory to determine the number and type of cells present and the amount of haematopoiesis (blood forming) activity taking place there. The diagnosis of JMML is confirmed by the presence of an excessive number of blast cells in the bone marrow.

Further testing

Once the diagnosis of JMML is made, blood and bone marrow cells are examined further using special laboratory tests. These tests provide more information about the exact type of disease your child has, the likely course of the disease and the best way to treat it.

Other tests may be conducted to provide information on your child’s general health and how their vital organs are functioning. These include a combination of further blood tests and imaging tests (x-rays, scans and ECG).

These results will provide a baseline of your child’s disease and general health, which will be compared with later results to assess how well your child is progressing and responding to treatment.