Sideroblastic anaemia: causes, symptoms, tests and treatment

Anaemia means the blood has fewer red cells or less haemoglobin than normal, so the body gets less oxygen. Great Ormond Street Hospital explains that in sideroblastic anaemia the body produces enough iron but cannot put it into haemoglobin, so a sideroblast, an immature red cell, accumulates an abnormally large amount of iron. In the bone marrow these cells show a ring of iron granules around the nucleus, which are called ring sideroblasts.

Patient.info's professional reference describes the sideroblastic anaemias as a heterogeneous group of inherited and acquired disorders characterised by anaemia of varying severity and the presence of ring sideroblasts in the bone marrow. Great Ormond Street describes it as a rare disorder.

Inherited forms are the less common. Patient.info says the most common inherited type is X-linked sideroblastic anaemia caused by mutations of the ALAS2 gene, and that the next most common involves SLC25A38. Great Ormond Street says some forms are inherited as an X-linked trait, which means they mainly affect males.

Acquired forms are more common in adults. The causes listed by Patient.info include myelodysplastic syndromes and other bone marrow diseases (myeloma, polycythaemia rubra vera, myelosclerosis, leukaemias), inflammatory conditions such as rheumatoid arthritis, chronic alcoholism, nutritional deficiencies such as copper and vitamin B6, lead poisoning and certain drugs. Great Ormond Street says some acquired forms are due to exposure to alcohol, lead or drugs and others appear for no reason (idiopathic) and tend to affect older people.

Blood Cancer UK describes MDS as a group of conditions in which the bone marrow does not make healthy blood cells, with symptoms caused by low levels of healthy blood cells that vary depending on which cells are affected. Some people with MDS do not need treatment straight away and go on active monitoring.

Patient.info says refractory anaemia with ringed sideroblasts may account for 5 to 15% of all MDS cases, and that acquired sideroblastic anaemia sometimes represents a stage in the development of MDS. This is why a haematologist will look carefully for reversible causes before concluding that it is an MDS subtype, and why clonal forms are followed over time.

Great Ormond Street lists weakness, fatigue and difficulty in breathing. The build-up of iron in the body can cause an enlarged spleen or liver and abnormal heart rhythms, and symptoms tend to be mild in childhood but become more severe in adulthood. Patient.info says there are no specific signs or symptoms related to sideroblastic anaemia alone.

• Tiredness, weakness and lack of energy.

• Breathlessness on exertion.

• Pale skin and, in some people, a fast heartbeat.

• An enlarged spleen or liver from iron overload.

• Irregular heart rhythms if iron overload is significant.

A full blood count usually shows anaemia, often with red cells that are small or of mixed size. The definitive step is a bone marrow examination. Patient.info says diagnosis is made from bone marrow examination demonstrating ring sideroblasts with a generalised increase in iron stores, and describes the condition as isolated erythroid dysplasia with fewer than 5% blasts and at least 15% ringed sideroblasts.

Your haematologist will also ask about alcohol, medicines, exposure to lead and diet, and will usually check vitamin B6, copper, B12 and folate where relevant, and sometimes genetic tests for inherited forms. The NHS explains that vitamin B12 and folate deficiency anaemias have their own symptoms and treatments, so these causes are distinguished from sideroblastic anaemia.

Treatment depends on whether the anaemia is inherited, due to a reversible cause or part of MDS. Great Ormond Street says there are various drugs used, including pyridoxine, that iron overload can be treated with deferoxamine, and that blood transfusions are also used.

Patient.info advises avoiding alcohol and reducing vitamin C intake because these increase iron absorption. Regular blood tests and ferritin checks monitor iron levels. People who need repeated transfusions need monitoring of the heart, liver and endocrine glands for iron damage.

The prognosis is very variable according to Patient.info. Contact your haematology team if you have increasing breathlessness, chest pain, palpitations or fainting, which may indicate severe anaemia or heart rhythm problems, and call 999 for chest pain, severe breathlessness or collapse.

On the NHS the pathway is through the GP or hospital haematology, with bone marrow tests and genetic services as needed. Treatment of MDS and rare anaemias is concentrated in specialist haematology centres, and children are managed by paediatric haematology teams.

A private haematologist can offer an earlier assessment or a second opinion, but bone marrow tests, transfusion and chelation are the same in both sectors, and long-term monitoring is usually shared with the NHS.