RESUMO
The alpha thalassaemia diseases in most cases are caused by deletions that affect one or two of the alpha genes, being less frequent the cases due to punctual mutations, insertions or deletions of a few pairs of bases, which have been denominated no deletion a thalassaemias. The objective of this investigation was to determine the incidence of the no deletion alpha thalassaemia in patients with a thalassaemia using molecular biology techniques. We studied 517 individuals of the San Carlos Hospital (Thalassemia Molecular Research Center, Madrid-Spain) between January 2001 and December 2003, in whom iron deficiency anemia had been ruled out, that presented microcytosis and hypochromia and that presented normal HbA2, HbF and EEF from normal Hbs. The two types of no deletion a thalassaemia most frequently described in the Mediterranean were studied: 1) alpha Hph due to deletion of 5bp in the IVS I and 2) alphaNco due to a change in the initiation codon of the gene. Of the 517 cases studied, 40 (7.7% of the cases) represented a no deletion alpha thalassaemia. Of these cases, 28 were positive for alphaHph of the alpha2 gene, 24 in the heterozygote state, one homozygote and three double heterozygotes associated with the 3,7 kb deletion. The remaining 12 cases were positive for the alphaNco of the alpha2 gene, 10 heterozygotes, one homozygote and one double heterozygote associated with the 4,2 kb deletion. The no deletion alpha thalassaemias represent < 8% from the cases in our environment. The alphaHph is the most frequent type of no deletion a thalassaemia and its haematological abnormalities are more manifest that the ones present in the cases of alphaNco.
Assuntos
Talassemia alfa/sangue , Talassemia alfa/genética , Deleção Cromossômica , Humanos , EspanhaRESUMO
Las a talasemias en la mayoría de los casos es debida a deleciones que afectan a uno o a los dos genes a, siendo poco frecuente los casos debidos a mutaciones puntuales, inserciones o deleciones de pocos pares de bases, los cuales se han denominado a talasemias no deleción. Se determinó la incidencia de la a talasemia no deleción en los pacientes con a talasemia, mediante biología molecular. Se estudiaron 517 individuos remitidos al Hospital Clínico San Carlos, centro de referencia de estudios moleculares de Talasemias en Madrid- España, entre Enero del 2001 a Diciembre del 2003, en los que se había descartado ferropenia y presentaban microcitosis, hipocromía, Hb A2, Hb F y EEF de Hbs normales. Se estudiaron los 2 tipos de a talasemia no deleción más descritas en el Mediterráneo: 1) aHph debida a la deleción de 5 bp en el IVS I y 2) aNco a un cambio en el codón de iniciación del gen. De los 517, 40 presentaban una a talasemia no deleción (7,7%). De éstos, 28 fueron positivos para aHph del gen a2, 24 en estado heterocigoto, 1 homocigoto y 3 dobles heterocigotos asociados con la deleción 3,7 kb. Los 12 restantes resultaron positivos para la aNco del gen a2, 10 heterocigotos, 1 homocigoto y 1 doble heterocigoto asociado con la deleción 4,2 kb. La a talasemia no deleción representa < 8% de los casos de a talasemia en nuestro medio. La aHph es el tipo de a talasemia no deleción más frecuente y cuyas anormalidades hematológicas son más manifiestas que las presentadas en los casos de aNco.
The a thalassaemia diseases in most cases are caused by deletions that affect one or two of the a genes, being less frequent the cases due to punctual mutations, insertions or deletions of a few pairs of bases, which have been denominated no deletion a thalassaemias. The objective of this investigation was to determine the incidence of the no deletion a thalassaemia in patients with a thalassaemia using molecular biology techniques. We studied 517 individuals of the San Carlos Hospital (Thalassemia Molecular Research Center, Madrid-Spain) between January 2001 and December 2003, in whom iron deficiency anemia had been ruled out, that presented microcytosis and hypochromia and that presented normal HbA2, HbF and EEF from normal Hbs. The two types of no deletion a thalassaemia most frequently described in the Mediterranean were studied: 1) a Hph due to deletion of 5bp in the IVS I and 2) aNco due to a change in the initiation codon of the gene. Of the 517 cases studied, 40 (7.7% of the cases) represented a no deletion a thalassaemia. Of these cases, 28 were positive for aHph of the a2 gene, 24 in the heterozygote state, one homozygote and three double heterozygotes associated with the 3,7 kb deletion. The remaining 12 cases were positive for the aNco of the a2 gene, 10 heterozygotes, one homozygote and one double heterozygote associated with the 4,2 kb deletion. The no deletion a thalassaemias represent < 8% from the cases in our environment. The aHph is the most frequent type of no deletion a thalassaemia and its haematological abnormalities are more manifest that the ones present in the cases of aNco.
