22nd May 2023

Aplastic Anaemia

Aplastic anaemia is a disease defined by pancytopenia caused by bone marrow insufficiency. The criteria for diagnosis of aplastic anaemia includes hypocellular bone marrow without abnormal cells or fibrosis, and at least two of:

• Hb <100 g/L
• Platelets <50 x 10⁹/L
• Neutrophils <1.5 x 10⁹/L

Symptoms are associated with depletion of each cell type:

• Anaemia – lethargy, pallor, dyspnoea, tachycardia
• Neutropenia – increased infections
• Thrombocytopenia – bleeding, bruising, petechiae

Causes of aplastic anaemia

The aetiology of aplastic anaemia is idiopathic in over 50% of cases but is thought to be immune-mediated. Other aetiologies that have been linked to aplastic anaemia include:

• Congenital – e.g. Fanconi anaemia, dyskeratosis congenita, Shwachman-Diamond syndrome
• Drugs – e.g. NSAIDs, chloramphenicol, carbamazepine, propylthiouracil
• Toxins – e.g. insecticides
• Viruses – parvovirus B19, hepatitis, EBV, CMV, HIV
• Ionising radiation
• Paroxysmal nocturnal haemoglobinuria

Treatment of aplastic anaemia

The main treatment options for aplastic anaemia include:

• Withdrawal of the cause, if known e.g. causative drug
• Supportive therapies e.g. blood product transfusion or antibiotics as required.
• Immunosuppression with steroid, antithymocyte globulin (ATG) and calcineurin inhibitor such as ciclosporin.
• Androgen therapy e.g. danazol
• Allogeneic stem cell transplantation
• Eltrombopag (oral thrombopoietin receptor agonist)

The choice of treatment depends on whether the aplastic anaemia is inherited or acquired, as well as its severity classification.

Inherited aplastic anaemia does not tend to respond to immunosuppression and therefore stem cell transplantation is considered first-line therapy, or androgen therapy if stem cell transplant is not an option. Androgen therapy can be complicated by hepatotoxicity and therefore regular monitoring of liver function tests and liver imaging is important.
Acquired non-severe aplastic anaemia can be monitored conservatively but may require immunosuppression with ATG and ciclosporin if transfusion dependent.

Acquired severe or very severe aplastic anaemia can be treated with a conditioning regimen and stem cell transplant from a matched related donor if availability and fitness allow. In patients over 50 or those without a matched related donor for stem cell transplant, then immunosuppression with ATG and ciclosporin is considered first-line
treatment.

Eltrombopag is an oral thrombopoietin receptor agonist which is currently approved for the treatment of patients with acquired severe aplastic anaemia, refractory to immunosuppressive treatment.