Prenatal Diagnosis of Hb H Hydrops Fetalis Caused By Haemoglobin Adana

α-Thalassaemia is the most common inherited disorder of Haemoglobin (Hb) production in southeast Asia, resulting from deficient synthesis of the α-globin chain component of the haemoglobin molecule due to deletion or inactivation of one or more of the normal four alpha-chain genes. The severity of the condition depends on the number of genes inactivated. The severest form is Hb Barts hydrops fetalis syndrome, due to loss of all 4 genes, which is generally incompatible with life. The mildest form is α+-thalassaemia trait due to inactivation of one gene which is completely asymptomatic, with loss of 2 or 3 genes resulting in cases of intermediate severity (i.e. 0, 1, 2 and 3 functional α−globin genes respectively) [1]. Rare variants of α-thalassaemia such as Hb Adana may be missed by the routine screening provided by the NHS and may need to be screened for in high prevalence population.