Overview
Sideroblastic anaemias are a group of conditions in which haemoglobin is insufficiently synthesised due to defective iron use, even if iron studies are normal/elevated. They are called sideroblastic due to ferritin accumulating in the mitochondria of immature red blood cells. These mitochondria form a ring around the nucleus and along with the deposition of ferritin, they form a ring sideroblast.
Sideroblastic anaemias can be congenital or acquired.
It may be helpful to look at the chapter on Anaemia: Data Interpretation alongside reading this section to help wrap your head around when to suspect what type of anaemia.
Epidemiology
- Acquired sideroblastic anaemia is more common
- Those with acquired sideroblastic anaemia often go on to develop myelodysplastic syndrome (MDS)
Causes
Congenital sideroblastic anaemia
- X-linked sideroblastic anaemia
Acquired sideroblastic anaemia
- Myelodysplastic syndrome
- Polycythaemia rubra vera
- Leukaemia
- Myeloma
- Systemic inflammation e.g. rheumatoid arthritis/systemic lupus erythematosus
- Lead poisoning
- Chronic alcohol excess
- Drugs – chloramphenicol and anti-tuberculosis medication
Example History
A 45-year-old man has tiredness that has been worsening over the last 6 months. On examination, he is pale. He has been on treatment for tuberculosis for the past 10 years.
Investigations:
| Haemoglobin: | 102 g/L | (130 – 180 g/L) |
| Platelets: | 205 x 109/L | (150 – 450 x 109/L) |
| Mean cell volume (MCV): | 75.0 fL | (76.0 – 98.0 fL) |
| White blood cells: | 8.5 x 109/L | (3.00 – 10.0 x 109/L) |
| Serum iron: | 15.3 μmol/L | (11.6 – 35.0 μmol/L) |
| Serum ferritin: | 370 ng/mL | (25 – 350 ng/mL) |
| Transferrin saturation: | 63 % | (20 – 50 %) |
| Blood film: | Basophilic stippling |
Presentation
There are no specific signs or symptoms of sideroblastic anaemia. Patients have general features of anaemia such as:
- Fatigue
- Pallor
- Dyspnoea
Investigations
Overview
- Full blood count (FBC):
- Haemoglobin low
- MCV: can be low/normal/increased
- Blood film:
- Hypochromic cells
- Basophilic stippling of red blood cells
- Basophilic stippling is a sign of disturbed erythropoiesis
- Haematinics:
- Serum iron: usually high
- Ferritin: usually high
- Transferrin saturation: usually high
- Bone marrow biopsy and examination:
- Shows ring sideroblasts and is diagnostic
Management
All patients
- 1st-line: supportive management with transfusions if necessary
- Patients should avoid alcohol and vitamin C intake as these can increase iron absorption
Prognosis
- Reversible causes such (e.g. alcohol) have a better prognosis if the underlying cause is managed
- Idiopathic sideroblastic anaemia and myelodysplastic syndrome have a median survival of around 3 years
- Idiopathic sideroblastic anaemia alone has a median survival of around 5 years
