We report a case of 12-year old Thai girl suffering
from mild non-transfusion-dependent thalassemia
intermedia. She is the single child in her
family. On examination she looked pale; there was
no hepatosplenomegaly. The Hb concentration
was 9 g/dL. Hb typing and molecular mutation
study revealed compound heterozygosity for HbE
and Hb Leiden (a2b2
6/7-Glu, codon 6/7-GAG). The
proportion of HbE was 47% whereas that of Hb
Leiden was 39%. The patient had no HbA. Hb typing
of her father and mother revealed HbE trait,
and no Hb Leiden was demonstrated. As the paternity
test confirmed the parenthood, we assume
that Hb Leiden has arisen by spontaneous mutation.
A study of the b-globin gene framework by
molecular cloning and subsequent DNA sequencing
of the b-globin gene in the members of the
family indicated that the Hb Leiden mutation
occurred on a maternal inherited chromosome.
The deletion of codon 6 or 7 (-GAG) of the b-globin
gene in the patient may be due to an unequal
crossing over during the mother’s oogenesis.