Aplastic anaemia in most cases is acquired, with no known cause. It is becoming increasingly recognised that inherited types of aplastic anaemia are more common than previously thought and can present in adults as well as children.

Aplastic anaemia classification

Aplastic anaemia can be very severe, severe, moderate or non-severe, depending on how low the numbers of the essential blood cells are. 

Very severe

• Neutrophils - less than 0.2 x 10⁹/L
• Platelets - less than 20 x 10⁹/L
• Bone marrow activity - less than 30 per cent

Severe

• Neutrophils less than 0.5 x 10⁹/L
• Platelets less than 20 x 10⁹/L
• Bone marrow activity less than 30 per cent

Non-severe

• All cases which do not follow the above classification.

Types of the relatively more common inherited aplastic anaemia are fanconi anaemia and dyskeratosis congenita .

Paroxysmal nocturnal haemoglobinuria (PNH) is closely linked to aplastic anaemia.