Acute promyelocytic leukaemia (APL): symptoms, diagnosis and treatment

Acute promyelocytic leukaemia is a rare and distinctive type of acute leukaemia. Cancer Research UK explains that AML starts from young white blood cells called granulocytes or monocytes in the bone marrow, and that it is divided into subtypes using the World Health Organization classification and into risk groups based on genetic changes. APL is one such subtype.

What sets APL apart is the genetic change driving it. NICE states that the disease is characterised by the t(15;17) translocation, also described as the PML/RAR-alpha gene. This genetic marker is part of why APL is managed with its own treatment pathway, including ATRA, which Cancer Research UK describes as related to vitamin A, rather than with the standard approach used for other forms of AML.

Because it is an acute leukaemia, it develops over weeks rather than years and needs specialist haematology care. The patient information from the NHS and Cancer Research UK on AML is the closest general UK patient guidance, and it is referred to throughout this page.

The NHS lists the main symptoms of AML as feeling very tired or weak, looking paler than usual, shortness of breath, bleeding or bruising easily or for no reason, getting ill a lot or taking longer than usual to recover, a high temperature, pain in the bones or joints, a swollen tummy and swollen glands. It adds that on brown or black skin paleness may be easier to see on the palms of the hands or inside the eyelids.

These symptoms are very common and have many causes, and having them does not mean you have leukaemia. The NHS advice is to ask for an urgent GP appointment or get help from NHS 111 if you have symptoms of acute myeloid leukaemia. It says the GP will usually arrange an urgent blood test if they think there is a chance of AML, and sometimes people have to go to hospital straight away.

• Tiredness, weakness and looking pale.

• Easy bruising or bleeding, or bleeding for no obvious reason.

• Repeated infections, or a high temperature.

• Bone or joint pain, a swollen tummy, swollen glands.

Cancer Research UK says most people start by seeing their GP, although some go to A&E depending on their symptoms. The doctor may suspect, or sometimes diagnose, AML from a blood test, and further tests are then done to confirm the diagnosis and learn more about the leukaemia. A GP should arrange a blood test or a referral to a blood specialist (haematologist) if symptoms could be due to AML.

For APL the specialist laboratory tests look for the characteristic genetic change. Identifying it quickly matters, because it determines which treatments are chosen. Your haematology team will explain which tests have been done and what they mean for your treatment plan.

The NHS says there are two main approaches to AML treatment: treatment which aims to cure (intensive treatment), usually given in hospital, and treatment which aims to control the leukaemia for as long as possible (non-intensive), usually at home with fewer side effects. Both involve chemotherapy and sometimes targeted medicines, and supportive treatments such as antibiotics and blood transfusions are also offered.

APL has a more specific pathway. NICE guidance TA526 recommends arsenic trioxide for inducing remission and consolidation in adults with untreated, low-to-intermediate risk APL when given with ATRA, and for relapsed or refractory disease after a retinoid and chemotherapy. NICE notes that people with untreated low-to-intermediate risk disease are otherwise given ATRA plus chemotherapy (together called AIDA), and that trial evidence shows arsenic trioxide plus ATRA is effective compared with AIDA.

NICE is open about the limits of the evidence in relapsed disease: the trial was small and did not compare arsenic trioxide directly with AIDA. A Cancer Research UK trial page describes the AML17 trial, a phase 3 study of treatment for APL in adults that ran from 2009 to 2013.

The NHS says AML is often treatable. Because survival depends on many factors, such as age, general health and risk group, Cancer Research UK points people to individual outlook information rather than a single figure, and this guide does not quote survival numbers for APL because the pages read did not give APL-specific figures.

During and after treatment you will have regular check-ups and sometimes tests and scans, according to the NHS, and you do not need to wait for your next check-up if you have symptoms or side effects that worry you. Cancer Research UK also provides information on diet, physical activity, fertility and emotional support after AML treatment.

Acute leukaemia is treated in specialist haematology units, and in the UK that is overwhelmingly through the NHS because treatment must begin quickly and relies on inpatient facilities, transfusion support and laboratory services. Private oncology cover may offer some choice of centre, but the treatment standards are the same national guidance, and your haematologist remains the best source of advice on your own situation.