I Polymorphism in Sickle Cell Disease in North Morocco.

Sickle cell disease is one of the most common severe monogenic disorders in the world. The -158 I polymorphism (C>T) of the γ-globin gene promoter is known to be associated with increased expression of the γ-globin gene, thus, higher production of Hb F and lesser clinical severity. This study aims to determine the frequency of the I polymorphism and its association with Hb F levels as a modulating factor of sickle cell disease severity in north Moroccan patients. Three hundred and eight subjects carrying the sickle cell mutation and 160 healthy individuals were recruited at the regional hospital of Larache, Morocco. The complete blood count and the Hb F levels were analyzed. The I polymorphism was determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique and statistical analysis were done using the Statistical Package for Social Sciences software version 20. Our results estimated the allelic frequency of the I polymorphism in our population at 15.8%. Out of 468 samples, 7.6% were homozygous [+/+] and 16.4% were heterozygous [+/-] for the I polymorphism. This polymorphism was revealed at 20.6% in SS patients, 24.2% in AS carriers, 28.6% in Hb S (: c.20A>T)/β-thalassemia (β-thal) patients and 22.5% in AA subjects. The north Moroccan sickle cell disease patients have shown a low frequency of the I polymorphism. This was later found to be associated with high Hb F levels and mild clinical severity.