Hereditary persistence of fetal haemoglobin

Heterogeneous groups of disorders caused by deletions or cross-overs involving b and g chain production, or non-deletional forms due to point mutations upstream of the g globin gene, with high levels of HbF production in adult life. There is 5 8 and b chain production with enhanced g chain production. Globin chain imbalance is much less marked than in b thalassaemia, resulting in milder disorder. There are few clinical effects.

May be pancellular (very high levels of HbF haemoglobin synthesis with uniform distribution in RBCs) or heterocellular (increased numbers of F cells).

Mechanism

Like 8b thalassaemia, HPFH frequently arises from deletions of DNA, which remove or inactivate the b globin gene (note: heterocellular HPFH may be result of mutations outside the b globin gene).

Heterozygous HPFH

Anaemia may be mild or absent. Haematological indices are normal. There is balanced a/non-a globin chain synthesis. HbF level ~25%.

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