How common is unexplained fever in acute lymphoblastic leukaemia?

Acute lymphoblastic leukaemia affects blood-forming cells in the bone marrow. It can leave the body less able to respond normally to infection, and fever may develop with an infection or with inflammation related to the illness. A temperature that comes and goes, returns after seeming to settle, or has no obvious explanation deserves attention. Many everyday viral and bacterial illnesses can also cause fever, so this symptom is not a diagnosis by itself.

Record the temperature, when it began, and accompanying symptoms such as chills, cough, sore throat, pain when passing urine, rash, bruising, unusual tiredness, or reduced appetite. Contact the clinical team promptly if the person has acute lymphoblastic leukaemia, is receiving treatment, or has been told their blood counts are low. Do not use a fever-reducing medicine to delay contacting the team; it can make the temperature harder to assess.

Seek urgent medical help for fever with confusion, severe weakness, breathing difficulty, chest pain, a stiff neck, a widespread rash, or inability to keep fluids down. A person having cancer treatment should follow the urgent-contact instructions given by their oncology service whenever a fever develops, even if they otherwise feel fairly well.

Ask what temperature should trigger an immediate call, whether any current treatment changes infection risk, and which medicines are appropriate while waiting for advice. It is also useful to ask whether blood tests or an examination are needed to look for infection or another cause.