Patients with sickle cell disease (SCD) produce significantly low levels of plasma nitric oxide (NO) during acute vaso-occlusive crisis. In transgenic sickle cell mice, NO synthesized by endothelial nitric oxide synthase (eNOS) enzyme of vascular endothelial cells has been found to protect the mice from vaso-occlusive events. Therefore, the present study aims to explore possible association of eNOS gene polymorphism as a potential genetic modifier in SCD patients. A case control study involving 150 SCD patients and age- and ethnicity-matched 150 healthy controls were genotyped by PCR-restriction fragment length polymorphism techniques for three important eNOS gene polymorphisms-eNOS 4a/b, eNOS 894G>T and eNOS -786T>C. It was observed that SCD patients had significantly higher frequencies of mutant alleles besides heterozygous and homozygous mutant genotypes of these three eNOS gene polymorphisms and low levels of plasma nitrite (NO2) as compared with control groups. The SCD severe group had significantly lower levels of plasma NO2 and higher frequencies of mutant alleles of these three SNPs of eNOS gene in contrast to the SCD mild group of patients. Haplotype analysis revealed that frequencies of one mutant haplotype '4a-T-C' (alleles in order of eNOS 4a/b, eNOS 894G>T and eNOS -786T>C) were significantly high in the severe SCD patients (P<0.0001), whereas the frequency of a wild haplotype '4b-G-T' was found to be significantly high (P<0.0001) in the SCD mild patients, which indicates that eNOS gene polymorphisms are associated with SCD patients in India and may act as a genetic modifier of the phenotypic variation of SCD patients.

MTHFR C677T and FVL G1691A polymorphisms may be risk factors for increased vascular complications in patient with SCD.

This study investigated the extent of molecular heterogeneity of the G6PD enzyme among certain aboriginal (tribal) populations of Orissa, an eastern Indian state, which is hyperendemic for Plasmodium falciparum malaria. A total of 3480 males from 14 tribal communities were screened, and 223 (6.4%) individuals were found to be G6PD deficient. Molecular analysis revealed that 59.2% of deficient individuals had the G6PD Orissa mutation and 37.2% had the G6PD Mediterranean mutation. The presence of G6PD Med has not been previously reported among the tribal populations of Orissa. Interestingly, both G6PD Med and G6PD Orissa were found among communities belonging to the Mundari (Austroasiatic) linguistic group, while G6PD Med was exclusive to Dravidian and G6PD Orissa to Indo-Aryan groups. Erythrocytic G6PD enzyme activity was severely reduced in the case of G6PD Med type (0.64-1.1 IU/g Hb) as well as among the uncharacterized samples, but was moderate in G6PD Orissa type (1.2-3.1 IU/g Hb). Anaemia was moderate among the individuals with G6PD Med mutation and mild among individuals with G6PD Orissa mutations. The prevalence of G6PD deficiency as well as molecular variants of the Gd- gene is highly heterogeneous among the tribal population of Orissa. The high endemicity of P. falciparum malaria has probably selected two different molecular variants of Gd- at different points in time, which is discussed.

Prevention of beta thalassaemia implies knowledge of the molecular spectrum occurring in the population at risk. This knowledge is necessary, especially when a prevention protocol is applied to a multiethnic population. For this purpose, we carried out molecular analysis of 431 beta thalassaemia subjects belonging to tribal (aboriginal) and non-tribal communities of Orissa, a part of peninsular India and found six types of mutation (four previously unreported and two reported). Molecular analysis of beta gene mutation showed that out of 431 beta thalassaemia cases (265 beta thalassaemia traits, 64 beta thalassaemia major, 47 haemoglobin E-beta thalassaemia, 55 haemoglobin S-beta thalassaemia cases), 71% of cases (n=306) showed the IVS I-5(G-->C) mutation, 12% of cases (n=52) showed FS 41/42(-CTTT), 7% of cases (n=30) showed CD 15(G-->A), 4.8% of cases (n=21) showed CD 30 (G-->C), 3% of cases (n=13) showed FS 8/9 (+G), and 2% of cases (n=9) showed IVSI-1(G-->T). The tribal populations possess only the IVS I-5(G-->C) mutation whereas the non-tribal groups possess the FS 41/42(-CTTT), FS 8/9 (+G), IVS I-1(G-->T), CD30(G-->C) and IVS I-5(G-->C) mutations. Among the non-tribal communities, Muslims did not have the IVS I-1 (G-->T) mutation. Clinically, anaemia was mild to moderate in beta thalassaemia trait and was found to be associated with the majority of abnormalities such as pyrexial episodes, fatigue, headache, lethargy and pallor. However, there were no differences in the incidence of clinical abnormalities between tribal and non-tribal populations and also among the different molecular variants of beta gene. This is the first report from Orissa on the prevalence of different molecular variants of beta thalassaemia. The clinical presentation of beta thalassaemia trait cases and their variation from other population have been discussed with reference to the different genetic variants.