The lower susceptibility to Plasmodium falciparum malaria of Fulani of Burkina Faso (west Africa) is associated with low frequencies of classic malaria-resistance genes.

The gene frequencies in 1993-94 for haemoglobin S, haemoglobin C, alpha-3.7 deletional thalassaemia, G6PDA-, HLAB*5301 were estimated in Fulani, Mossi and Rimaibé ethnic groups of Burkina Faso, West Africa. The aim of the study was to verify whether the previously reported Fulani lower susceptibility to Plasmodium falciparum malaria was associated with any of these malaria-resistance genes. Similar frequencies for haemoglobin S were recorded in the 3 ethnic groups (0.024 +/- 0.008, 0.030 +/- 0.011, 0.022 +/- 0.013; in Mossi, Rimaibé and Fulani, respectively). The Mossi and Rimaibé showed higher frequencies when compared to Fulani for haemoglobin C (0.117 +/- 0.018, 0.127 +/- 0.020, 0.059 +/- 0.020), alpha-3.7 deletional thalassaemia (0.227 +/- 0.040, 0.134 +/- 0.032, 0.103 +/- 0.028), G6PDA- (0.196 +/- 0.025, 0.187 +/- 0.044, 0.069 +/- 0.025) and HLA B*5301 (0.189 +/- 0.038, 0.202 +/- 0.041, 0.061 +/- 0.024). Among Fulani the proportion of individuals not having any of these protective alleles was more than 3-fold greater than in the Mossi-Rimaibé group (56.8% vs 16.7%; P < 0.001). These findings exclude the involvement of these genetic factors of resistance to P. falciparum in the lower susceptibility to malaria of Fulani. This evidence, in association with the previously reported higher immune reactivity to malaria of Fulani, further supports the existence in this ethnic group of unknown genetic factor(s) of resistance to malaria probably involved in the regulation of humoral immune responses.

Detection of alpha-globin gene disorders by a simple PCR methodology.

BACKGROUND: alpha thalassemias are very common in all thalassemic areas; however, complete knowledge of the phenotypic, genotypic and epidemiological features of these thalassemias has not yet been achieved for a number of reasons: the frequent absence of a thalassemic hematologic picture, the lack of a specific characteristic comparable to the Hb A2 increase for beta thalassemias, and the almost complete homology between the two alpha genes. METHODS AND RESULTS: A new set of PCR techniques, each based on primer(s) specific for a particular type of alpha globin gene disorder, has been devised in our laboratory. The procedures are simple, and non-radioactive. They lead to the identification of all alpha globin disorders common in the Mediterranean area [-alpha 3.7, -alpha 4.2, alpha Hphl, alpha Ncol, --MED, -(alpha)20.5, alpha alpha alpha anti3.7]. The electrophoretic patterns specific for the main alpha globin alterations as observed with this set of techniques, are presented. CONCLUSIONS: Owing to their advantageous properties, these techniques are suitable for precise molecular characterization of the numerous subjects selected through mass population screenings.

Cardiovascular involvement in thalassaemic patients with pseudoxanthoma elasticum-like skin lesions: a long-term follow-up study.

BACKGROUND: Congenital haemolytic anaemia may be associated with pseudoxanthoma elasticum (PXE)-like clinical manifestations. METHODS: The cardiovascular system of 14 homozygous and double heterozygous beta-thalassaemia patients with skin and retinal vessel alterations similar to those in genetic PXE was analysed over a period of 12 years and compared with that of 13 relatives (five sets of parents, one single parent, two thalassaemic brothers), and that of the control group composed of 16, age- and sex-matched, thalassaemic patients. RESULTS: All patients with clinical PXE-like skin lesions exhibited, by light and electron microscopy, dermal alterations and mineralization of elastic fibres identical to those typical of inherited PXE. None of the relatives and none of the control group showed clinical or structural findings of PXE. The follow-up started in 1988. After 12 years of clinical observation, six patients showed dramatic progression of skin involvement, angioid streaks had progressed in two subjects. One patient had recurrent gastrointestinal bleeding and underwent partial stomach removal for gastric artery aneurysm, one underwent colon resection for intestinal infarct, one patient had a transitory ischaemic attack, one died after an intracranial haemorrhage, two patients died from cardiovascular disease and one from neoplasia. CONCLUSIONS: Thalassaemic patients with PXE-like skin lesions also manifest PXE-like vessel alterations that progress with time. Considering the severe outcome of these lesions, accurate monitoring should be routinely performed on the cardiovascular system of thalassaemic patients with PXE-like skin manifestations.

Silent thalassemias: genotypes and phenotypes.

BACKGROUND AND OBJECTIVE: Current application of molecular biology techniques to the study of the DNA of globin genes has confirmed the existence of silent alpha and beta thalassemias; which had already been reported on the basis of red blood cell parameters and family studies. The present work was aimed at analyzing all the aspects of the phenotype of the most common varieties of silent thalassemia. MATERIALS AND METHODS: Groups of heterozygous carriers of these varieties were examined using established techniques that determined all hematologic, hemoglobin (electrophoresis and measurement of Hb A2 and Hb F levels), and globin synthesis (evaluation of the alpha/beta ratio) parameters. Furthermore, all subjects underwent a complete molecular study of the alpha and beta globin genes by means of the ARMS, SSCP, DGGE, PCR and Southern blotting techniques. RESULTS: 1) The -101 C-->T mutation of the promoter of the beta globin gene shows a normal hematological picture with the Hb A2 level often slightly raised and the alpha/beta globin synthesis ratio slightly greater than 1; 2) beta + thalassemia resulting from the IVS II 844 C-->G mutation has a phenotype that is even closer to normal; 3) -alpha 3.7 deletion type I usually has a totally silent phenotype; 4) the alpha Ncol mutation almost always gives rise to a sub-silent phenotype if it is located on gene alpha 2 and to a silent phenotype if it is found on gene alpha 1; 5) alpha + thalassemia due to the alpha 2 Hphl mutation displays a sub-silent phenotype in some cases and a silent one in others; 6) triplication of the alpha genes gives rise to a phenotype that is quite similar to that of the -101 C-->T mutation of the promoter of the beta globin gene, namely one that is very often silent. INTERPRETATION AND CONCLUSIONS: Many of these silent varieties (beta + thalassemia due to the -101 C-->T mutation; alpha + thalassemia from a deletion or point mutation of an alpha gene; alpha alpha alpha triplication) are quite frequent in the overall group of thalassemias. It is therefore important for the operators in the field of thalassemia diagnosis to possess exact knowledge of them especially in order to prevent thalassemia major.

Phenotypes of individuals with a beta thal classical allele associated either with a beta thal silent allele or with alpha globin gene triplication.

BACKGROUND AND OBJECTIVE: beta thalassemia intermedia has its origins in compound heterozygosity for many different beta thal defects or in an interaction of a beta thal defect with altered alpha cluster. Two specific genetic associations (beta thal/beta(+) -101 C-->T and beta thal + alpha alpha alpha or alpha alpha alpha alpha) have been described in recent years as being determining a phenotype similar to that of simple beta thal heterozygote or, alternatively, a clinical picture of thalassemia intermedia. METHODS: A detailed study on this subject was carried out on 55 patients divided into 2 groups. Group I consisted of 20 patients, 17 of whom (Group Ia) had a beta thal/beta(+) -101 C-->T genotype and 3 (Group Ib) had a beta thal/beta IVS II-844 C-->G genotype. Group II consisted of 35 patients with beta thal association + alpha alpha alpha or alpha alpha alpha alpha. The methods of study have already been described in a previous issue. RESULTS: Thirty percent of group Ia and 25% of group II were virtually asymptomatic, while the others presented the thalassemia intermedia phenotype. This second phenotype is generally milder in patients of group I and even less so in those of group II. In the former there is a higher level of HbF; in the second there is more marked alpha/beta + gamma globin synthesis imbalance. The severity of the phenotype has no connection with that of the beta thal defect. The patients of group Ib all presented thalassemia intermedia. INTERPRETATION AND CONCLUSIONS: The definite clinical pictures of groups I and II are quite common in the Italian population and should therefore be well understood, especially for proper application of preventive measures against thalassemia major.