Webster's New World Medical Dictionary

thalassemia, alpha
A form of thalassemia that
involves the hemoglobin alpha chain. If a fetus
inherits two genes for alpha thalassemia, one from
each parent, the disorder is lethal before birth: No
alpha chains can be made, and without alpha
chains, there can be no fetal hemoglobin. If the
fetus inherits only one alpha thalassemia gene, it
will survive and have no or few symptoms as a child,
as there is another gene that is still able to make
alpha chains. See also 
thalassemia.
thalassemia, beta
See 
thalassemia major.
thalassemia major
The most serious form of
beta thalassemia, in which there is a mutation in
both of the beta globin chains of hemoglobin. This
leads to underproduction or absence of beta chains,
underproduction of hemoglobin, and profound
anemia. Children with thalassemia major seem
entirely normal at birth because at birth they still
have predominantly fetal hemoglobin, which does
not contain beta chains. The anemia emerges in the
first few months of life and becomes progressively
more severe, leading to pallor, fatigue, failure to
thrive, bouts of fever due to infections, and diar-
rhea. The gene for thalassemia major is relatively
frequent in people of Mediterranean origin.
Children with thalassemia major inherit one tha-
lassemia gene from each parent. Treatment based
on blood transfusions is helpful but not curative.
Also known as beta thalassemia, Cooley anemia, and
Mediterranean anemia. See also 
thalassemia.
thalassemia minor
Also called thalassemia trait,
the carrier state for thalassemia major. People who
are carriers have just one beta thalassemia gene and
are essentially normal, although they can transmit
the gene to their offspring. See also 
thalassemia.
thalidomide
A drug (brand name: Thalomid)
that was used in the 1950s and early 1960s to treat
morning sickness in pregnancy. The use of thalido-
mide had tragic results: When taken during preg-
nancy, it can cause a syndrome of congenital
malformations in the developing fetus. Thalidomide