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Medical glossary

Philadelphia chromosome

The Philadelphia chromosome (Ph) is a shortened chromosome 22 formed when pieces of chromosomes 9 and 22 swap places. It is named after the city where it was discovered.

Last updated: ~1 min read
Stained chromosomes of a dividing cell on a dark background under the microscope
Figure 1.The Ph chromosome is found by studying the chromosomes

01Short answer

This translocation, t(9;22), creates the BCR::ABL1 fusion gene. Ph is found in almost all cases of CML and in some cases of ALL (Ph-positive ALL). Ph is not inherited; it arises in the leukaemia cells during life. Its presence makes targeted treatment with TKIs possible. It is detected by karyotype, FISH and PCR.

02Simple explanation

Chromosomes 9 and 22.

An acquired change.

CML and some ALL.

A TKI target.

03Scientific explanation

NCI: the Philadelphia chromosome is an abnormality formed when parts of chromosomes 9 and 22 switch places.

The NCI Dictionary explains cancer terms in plain language; check the exact meaning for your situation with your doctor.

04What happens in the body?

How it is found

Karyotype, FISH and PCR.

A shortened chromosome
Figure 2.A shortened chromosome.

Why it matters

It makes targeted treatment possible.

A city
Figure 3.A city — Philadelphia chromosome

Where you will see this word

In test results, discharge letters and conversations with your doctor. Write the word down and ask what it means.

Ask your doctor

The general meaning and the meaning of your own result can differ. The most important question is “What does this mean for me?”

05From an unfamiliar word to a clear answer: four steps

Write it down, look it up, prepare a question, ask.

Write it down — From a result or a conversation.1Write it downFrom a result or a conversation.
Look it up — Learn the plain meaning.2Look it upLearn the plain meaning.
Prepare a question — What does this mean for me?3Prepare a questionWhat does this mean for me?
Ask — Your doctor gives the personal explanation.4AskYour doctor gives the personal explanation.
UnderstandingResults feel less frightening.
ConversationA shared language with your doctor.
SafetyNot drawing conclusions alone.

06Key points at a glance

TopicIn brief
How it is foundKaryotype, FISH and PCR.
Why it mattersIt makes targeted treatment possible.
Where you will see this wordIn test results, discharge letters and conversations with your doctor. Write the word down and ask what it means.
Ask your doctorThe general meaning and the meaning of your own result can differ. The most important question is “What does this mean for me?”

07Key terms

Ph+
Philadelphia chromosome-positive.
t(9;22)
A translocation between chromosomes 9 and 22.
Term
A word with a precise medical meaning.
Reference range
The range a laboratory considers normal.

08Key points

  • Learn.
  • Ask your doctor.
  • Write it down.
  • Write the word down.
  • Ask what it means.

09Frequently asked questions

Will my children inherit it?

No, it is not an inherited change.

What is Ph-positive ALL?

A type of ALL with Ph; a TKI is added to treatment.

This word is in my results: should I worry?

The word itself does not mean a serious or mild condition; get the explanation from your doctor.

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. Will my children inherit it?

  2. What is Ph-positive ALL?

  3. This word is in my results: should I worry?

My questions

12Sources

  1. National Cancer Institute. NCI Dictionary of Cancer Terms: Philadelphia chromosome
  2. National Cancer Institute. Chronic Myelogenous Leukemia Treatment (PDQ®) – Patient Version
  3. National Cancer Institute. Adult Acute Lymphoblastic Leukemia Treatment (PDQ®) – Patient Version
  4. National Cancer Institute. NCI Dictionary of Cancer Terms
  5. National Cancer Institute. Leukemia
  6. MedlinePlus. Complete Blood Count (CBC)
  7. NHS. Sepsis
  8. National Cancer Institute. NCI Dictionary of Cancer Terms: remission
  9. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: blast
  10. National Cancer Institute. NCI Dictionary of Cancer Terms: absolute neutrophil count
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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