Genotyping the HFE gene by melting point analysis with the LightCycler system: Pros and cons

The assay that combines rapid-cycle PCR with allele-specific fluorescent probe melting profiles performed on the Roche Diagnostics LightCycler is commonly employed for genotyping the HFE gene. We report three illustrative cases of the pros and cons of this method. In two cases, atypical melting curves allows the identification of new DNA substitutions in the HFE gene, whereas, in the third case, a typical melting curve of c.845G>A mutation (C282Y) homozygosity overlooks a nucleotide change and promotes misdiagnosis of HH.

Autosomal dominant hereditary hemochromatosis associated with two novel Ferroportin 1 mutations in Spain

Hereditary hemochromatosis is a common disorder of iron metabolism most frequently associated with mutations in the HFE gene. Hereditary hemochromatosis may be caused by other genetic mutations including those in the SLC40A1 gene. This report describes the clinical and laboratory findings of two Spanish families with autosomal dominant iron overload associated with previously unrecognized Ferroportin 1 mutations (p.R88T and p.I180T). The phenotype of iron overload in the patients carrying these mutations could correspond to the group of clinical mutations that lose their iron export function.

Measurement of liver iron overload by magnetic induction using a planar gradiometer: preliminary human results

The measurement of hepatic iron overload is of particular interest in cases of hereditary hemochromatosis or in patients subject to periodic blood transfusion. The measurement of plasma ferritin provides an indirect estimate but the usefulness of this method is limited by many common clinical conditions (inflammation, infection, etc). Liver biopsy provides the most quantitative direct measurement of iron content in the liver but the risk of the procedure limits its acceptability. This work studies the feasibility of a magnetic induction (MI) low-cost system to measure liver iron overload. The excitation magnetic field (B0, frequency: 28 kHz) was produced by a coil, the perturbation produced by the object (deltaB) was detected using a planar gradiometer. We measured ten patients and seven volunteers in supine and prone positions. Each subject was moved in a plane parallel to the gradiometer several times to estimate measurement repeatability. The real and imaginary parts of deltaB/B0 were measured. Plastic tanks filled with water, saline and ferric solutions were measured for calibration purposes. We used a finite element model to evaluate the experimental results. To estimate the iron content we used the ratio between the maximum values for real and imaginary parts of deltaB/B0 and the area formed by the Nyquist plot divided by the maximum imaginary part. Measurements in humans showed that the contribution of the permittivity is stronger than the contribution of the permeability produced by iron stores in the liver. Defined iron estimators show a limited correlation with expected iron content in patients (R < or = 0.56). A more precise control of geometry and position of the subjects and measurements at multiple frequencies would improve the method.

[Interest in the study of genetic variants of the promoter region of the UGT1A1 gene in neonatal jaundice]

BACKGROUND

A relationship between polymorphism in the promoter region of the UGT1A1 gene (associated with Gilbert's syndrome) and the development of jaundice has recently been demonstrated. This polymorphism is due to (TA)7 instead of wild-type (TA)6.

OBJECTIVE

To investigate the relationship between Gilbert's syndrome and neonatal jaundice by evaluating the distribution of (TA)7 in a population of newborns.

METHODS

A total of 136 newborns were studied: 21 had neonatal jaundice, 69 were healthy and the remaining newborns had various diseases. DNA from each patient was used to amplify, by polymerase chain reaction, the promoter region of the UGT1A1 gene, which flanks the TATA box where the polymorphism is located.

RESULTS

In the group without jaundice, 53 % of the newborns were normal (6/6 genotype), 40 % were 6/7 and 7 % were 7/7. In the group with jaundice, 33 % of the newborns were normal, 53 % were heterozygous (6/7) and 14 % were homozygous (7/7). Comparison of the groups revealed that the prevalence of UGTA1A polymorphism tended to be greater among jaundiced newborns (p 0.09).

CONCLUSION

The results of this study suggest that there is a relationship between neonatal jaundice and Gilbert's syndrome among the Spanish population. These results, together with those of other authors, suggest that genetic screening for Gilbert's syndrome should be included in the investigation of neonatal jaundice in our population. Further studies with a greater number of subjects would determine the exact relationship between marked neonatal jaundice and IGTA1A polymorphism. Key words:

[Molecular study of red cell pyruvate kinase deficiency in 15 patients with chronic hemolytic anemia. Group of Erythropathology of Hematology and hemotherapy Association of Spain (HHAS)]

BACKGROUND

Identification of RBC pyruvate-kinase (PK) gene mutations by polymerase chain reaction (PCR) and single strand conformation polymorphism (SSCP) followed by PK gene sequencing in positive cases has been assessed and the results obtained with a preliminary study of 15 unrelated patients of Spanish origin are presented.

PATIENTS AND METHODS

Patients have been classified into two different groups: group 1, propositus (15 cases), and group 2, relatives of the patients included in group 1 (10 males and 5 females). In group 1, a PCR was followed by SSCP and sequencing, and in group 2, the PCR was followed by digestion with specific restriction endonucleases (PCR-ER).

RESULTS

Group 1: from 15 patients included in the study 2 were identified as homozygous, 4 as heterozygous and 9 as compound heterozygous. In this group, were identify 26 affected alleles with 11 different mutations: T1456 10 alleles (38.6%), T721 3 alleles (11.6%), A1010, C514, C1015 and T1223 2 alleles (7.7%), and C1070, A1291, T1508, A1595 y T1675 one allele. Relatives from 8 out of 15 patients from group 1 showed the following pattern: homozygous (one case), heterozygous (10 cases), compound heterozygous (2 cases) and normal (2 cases).

CONCLUSIONS

SSCP procedure followed by direct gene sequencing in positive cases is fast and simple enough to allow the identification of PK deficient variants, avoiding the need of biochemical characterisation of semipurified deficient enzyme, which is more cumbersome and time consuming. In addition, the PCR-ER method is a very useful tool for screening of the most frequent molecular variants, as well as, for the detection of the carrier condition of this enzymopathy (family studies).

Molecular characterization of the PK-LR gene in pyruvate kinase deficient Spanish patients. Red Cell Pathology Group of the Spanish Society of Haematology (AEHH)

The PK-LR gene has been studied in 12 unrelated patients with red cell pyruvate kinase deficiency and hereditary nonspherocytic haemolytic anaemia (CNSHA). The entire codifying region of the R-type PK gene and the flanking intronic regions were analysed by single-stranded conformation polymorphism (SSCP) followed by direct sequencing of abnormal DNA. 10 different mutations were identified in 22/24 alleles at risk. Eight of these were missense mutations that caused the following single amino acid changes: G514C (172Glu-Gln), G1010A (337Arg-Gln), G1015C (339Asp-Gln), T1070C (357Ile-Thr), C1223T (408Thr-Ile), G1291A (431Ala-Thr), C1456T (486Arg-Trp) and G1595A (532Arg-Gln). Two were nonsense mutations: G721T (241Glu-Stop) and C1675T (559Arg-Stop). 7/22 alleles demonstrated the same C1456 --> T mutation. The study of the polymorphic site at nucleotide (nt) 1705 performed in all cases disclosed a 1705 C/C mutation in 10 and a 1705 A/C mutation in three. This is the first report on the presence of several different L-type PK gene mutations within Spanish population. Furthermore, from the PK gene mutations found, six were unique and not previously described (1015C, 1070C, 1223T, 1291A, 1595A and 1675T) and one (C1456T) seems to be predominant in Spain. Interestingly, no case with the 1529A mutation commonly found in Northern European populations was present here.

[Molecular analysis of glucose-6-dehydrogenase deficiency in Spain]

PURPOSE

G6PD deficiency is the most frequent enzymopathy-producing genetic polymorphism in humans. Up to now, over 400 putative variants of G6PD have been distinguished on the basis of biochemical characterization of the deficient enzyme. Analysis of the G6PD gene has made possible a precise classification of the G6PD molecular variants by identification of about 80 different point mutations causing much of the phenotypic heterogeneity. In the Spanish population, the analysis of G6PD has led to the identification of 15 different point mutations that underlay the phenotypic heterogeneity of G6PD previously reported by biochemical analysis. The purpose of the study has been to identify the genetic mutation responsible of the G6PD deficiency and to improve the knowledge of its genetic homogeneity.

PATIENTS AND METHODS

From 50 Spanish males with G6PD deficiency 34 came from out consultation and 16 from the Spanish Study Group on Red Cell Pathology (GEHBTA-Eritropatología) The methods employed included screening of prevalent mutations by ER-PCR, SSCP-PCR, genetic segmentation and biochemical characterization of the deficient enzyme.

RESULTS

In 31 cases the mutations were characteristic of the four most frequent polymorphic variants found in Spain (G6PD A-376G/202A, G6PD Mediterranean 563T G6PD Union 1360T and G6PD Seattle 344C). Since these mutations either create or abolish a specific site recognized by a restriction endonuclease (RE), they can be rapidly detected by RE digestion of a PCR-amplified product (PCR-RE). In patients where none of these mutations were present (17 cases), the G6PD gene was subjected to PCR single-strand conformation polymorphism (PCR-SSCP) analysis combined with direct PCR-sequencing. By using this procedure, 9 new mutations have been identified, five of them have been also found in other geographical areas and were associated with favism (G6PD A-376G/968C, G6PD Santamaria 376G/542T, G6PD Aures 143C and G6PD Chatham 1003A) or chronic haemolytic anaemia (G6PD Tomah 1153C). The other four mutations are unique and not reported so far: Three of them are associated with favism (G6PD Málaga 542T, G6PD Murcia 209G and G6PD Valladolid 406T) and one with chronic haemolytic anaemia (G6PD Madrid 1155G). The remaining eight cases are under study.

CONCLUSION

The present study confirms the marked genetic heterogeneity of G6PD deficiency in Spain and demonstrate that the PCR-RE analysis is an easy tool for rapid diagnosis of the molecular defect in subjects with the common forms of G6PD deficiency. Furthermore the fact that G6PD A-376G/202A is the most common variant within Spanish population and the finding of G6PD Aures 43C and G6PD Santamaría 76G/542T, who are polymorphic in Algeria is consistent with a significant gene flow from Africa to Europe through Spain.

[Hematologic deficiencies in patients with recurrent oral aphthae]

BACKGROUND

The prevalence of iron, folic acid and vitamin B12 deficiencies and their role in the development of recurrent oral ulcerations is not well known. The aim of this study was to determine the prevalence of these deficiencies in our patients.

PATIENTS AND METHODS

Iron, folic acid and vitamin B12 levels were studied in 80 patients with recurrent oral ulcerations (ROU) and the results were compared with a control group of 29 patients with different oral diseases.

RESULTS

In the recurrent oral ulcers patients, deficiencies were detected in 21/80 patients (26.2%). In 18 cases they were pure: iron (4), folic acid (10) and vitamin B12 (4). In 3 patients, combined deficiencies were detected, being secondary to pernicious anaemia in two patients. In the control group, deficiencies were observed in 4/29 cases (13.7%). In three cases they were isolated (one case suffered from ferropenic anaemia and two patients of pernicious anaemia).

CONCLUSIONS

Patients with recurrent oral ulcerations have more frequently iron, folic acid and vitamin B12 deficiencies than those with other diseases of oral mucosa. However, there were not significant differences when the frequency of deficiency of each one of such elements were taken into account separately.

[Standardization Committee for Haematology. External Quality Assurance Program for General Hematology. Evaluation of the 1994 results]

Since 1994, the Standardisation Committee for Haematology publishes yearly the results of its external quality assurance programme (EQAPH), after it has been improved and even integrated in the Health Services of some autonomous communities.

METHODS

Four hundred and seventy-three laboratories take part in EQAPH. The evaluation of the haematological records is carried out every year from the results of two whole blood samples. Two samples of lyophillised plasma are sent every month to participant laboratories in order to assess prothrombin time (PT), partial thromboplastin time (PTT) and fibrinogen. Samples are sent every three months for antithrombin III (AT-III) determination. According to the types of autoanalysers used, 9 groups have been established: Group I (Technicon H* and H-6000), group II (Technicon H*2 and H*3), group III (Coulter MaxM, STKS, Cobas Argos and Cell-Dyn 3000/3500), group IV (Coulter STKR), group V (Coulter JS/JT), group VI (Coulter S/T, Cobas Helios/Minos), group VII (Sysmex E/NE), group VIII (Sysmex K-1000), and group IX (other semi-automated counters). Three groups are established for general coagulation tests and two others for AT-III. The value of the mean of all results (consensus mean) and of each particular group (group mean) are used as statistical methods. The results are expressed as: (1) coefficient of variation, % (CV); (2) deviation index (DI); DI values attained with respect to the same group (or method) or all groups (or methods) allowed us to classify the results in four categories: excellent (0 < DI < 0.5), good (0.5 < DI < 1.0), satisfactory (1.0 < DI < 2.0), and out of acceptable limits (ID > 2.0); (3) Youden graphs or graphic representations of DI calculated from the analysis of the control specimens.

RESULTS

Group I yielded lesser values for leucocyte count (0.221) and higher for MCH (0.833). Group II showed high DI values for PCV (0.933) and MCV (1.146). Group III had lower values for red cell count (0.097), haemoglobin concentration (0.133) and MCH (0.91). Group IV showed lower platelet count. Group V had higher haemoglobin concentration values. Group VI yielded higher DI in the platelet count and group VII in the white cell count. Group VII showed the lowest DI for MCV and MHC. Group IX had high values for red cell count and MCH. In the coagulation field, group I had higher values for PT and AT-III. Group II showed higher DI values for PTT and fibrinogen. The highest CV values were seen in groups VIII and IX. The lowest values were present in group II for haemoglobin, IV for MCH, in V for PCV and MCV, in VII for red cell count and MCH, in VII for white cell count and in VII for platelet count. The coagulation tests showed lower CV values than cytometry, the lowest being for PT in group I and PTT and fibrinogenein group II. With regard to the influence of acceptable results on adverse ones within this group, the percentage of laboratories with mean DI over 2 were calculated. Thus, the laboratories achieved 43.5% of values within acceptable limits for platelet count and 56.7% for white cell count. Regarding the PCV, out of 47.9% of the laboratories, only 1.0% showed high deviation of some results. In the coagulation parameters, of the 37.2 in this group for AT-III, 32.4% showed a mean DI over 2.

CONCLUSIONS

Participation in External Quality Assurance programmes contributes to the comparability of the results provided by different laboratories, thus increasing their accuracy and improving the quality of patient care.

The deoxyuridine suppression test in HIV-1 positive patients: the role of azydothymidine (AZT)

The deoxyuridine suppression test (dUST) was used to evaluate human immunodeficiency virus type 1 positive (HIV-1) patients with low serum levels of vitamin B12 and/or low red cell folate and to assess any possible interferences of azydothymidine (AZT) in this test. The dUST was studied in 29 HIV-1 positive patients, 18 without low serum vitamin B12 or low red cell folate and 11 with low serum vitamin B12 (6 patients), low red cell folate (4 patients) and 1 case with both. The role of AZT was studied using different concentrations (0.2, 2.5 and 10 microM/ml) in 2 groups: 1 group of 5 patients with vitamin B12 and/or folate deficiency and another group consisting of 13 healthy subjects. Methotrexate (MTX)(50 micrograms/ml) was added to induce a folate megaloblastic pattern in the latter group. Results of the dUST in the HIV-1 group without low levels of serum vitamin B12 fell within the health-related reference interval values. A vitamin B12 deficiency was only detected in 1 case in the HIV-1 group with low serum vitamin B12, although a folate deficiency pattern was observed in the 4 patients with low red cell folate. In the healthy subjects AZT induced a dose-dependent decrease of the MTX-induced folate megaloblastic pattern. The pattern was also observed in the group of patients with vitamin B12 or folate deficiency, although AZT did not entirely interfere with the dUST. The effect of AZT on the dUST was attributed to a decrease in the incorporation of the isotope in the absence of deoxyuridine. The dUST is useful in differentiating vitamin B12 deficient patients from HIV-1 infected patients with low levels of serum vitamin B12.

Prevalence of high serum and red cell ferritin levels in HIV-infected patients

We report a high prevalence of elevated serum and red cell ferritin (SF and RCF) levels in 168 patients with HIV infection. SF levels increase with clinical worsening of infection and with decreasing CD4+ lymphocyte counts (ANOVA, p < 0.001) while RCF is significantly higher in asymptomatic AIDS patients (ANOVA, p < 0.001) and in those treated with zidovudine (AZT) (ANOVA, p < 0.001). It is suggested that, although inflammatory processes may explain high SF levels, if we also take in account RCF levels a possible association between iron overload and HIV infection might exist, and this may be worsened by AZT treatment. The significance of these high ferritin levels and their effects on immune system suppression and susceptibility to infectious and neoplastic complications in these patients merits further investigation.

[Pernicious anemias with subtle or atypical presentation]

PURPOSE

To assess the prevalence and clinico-biologic characteristics of pernicious anaemia (PA) showing subtle or atypical onset.

MATERIAL AND METHODS

One-hundred and twenty-four patients were found to fulfill criteria for PA (serum vitamin B12 deficiency due to absence of intrinsic factor secretion because of severe gastric atrophy). Of them were disclosed those lacking macrocytosis (MCV less than 98 fL), with or without anaemia (Hb less than 120 g/L in women and less than 14 f/L in men), but showing decreased serum B12 rates (less than 150 pmol/L).

RESULTS

Macrocytosis was absent in 15 out of the 124 cases (12.1%); either they had anaemia or not, serum B12 rates were decreased in all cases. Eight patients had concurrent iron deficiency, one had secondary anaemia, two had polycythaemia and four were normal from a haematological standpoint. Serum B12 assays were performed because of neuropsychiatric impairment (2 cases), polycythaemia study (3 cases), or positive anti-parietal cell antibodies found in an immunologic study (4 cases). The remaining patients were studied for chronic atrophy of the gastric mucosa (2 cases), and Plummer-Vinson syndrome, leucopenia and nutritional assessment (1 case of each condition).

CONCLUSIONS

Atypical presentation of pernicious anaemia, whose frequency is probably underestimated, was confirmed in our environment. This condition must be suspected and ruled out in patients with characteristics similar to those described above.

The deoxyuridine suppression test in peripheral lymphocytes

The effects of different deoxyuridine (dU) concentrations on lymphocytes stimulated with phytohemagglutinin (PHA) were studied for use in a lymphocyte dU suppression test (L-dUST). High concentrations of dU were necessary to overcome the unspecific spontaneous pattern of folate deficiency, dU suppression tests with cells of bone marrow (BM-dUST) and with lymphocytes were carried out in 15 patients with vitamin B-12 deficiency, in 12 with folate deficiency, and in 10 with other pathological conditions. L-dUST was also carried out in 15 healthy reference controls. The BM-dUST was able to distinguish patients with vitamin B-12 or folate acid deficiencies from those without, while the L-dUST was unable to do so in most cases. L-dUST does not, therefore, appear to be a reliable method for the diagnosis of megaloblastic changes.

Different lymphocyte activity in patients with polycythaemia vera versus secondary polycythaemia and healthy blood donors

On comparing lymphocyte patterns in patients with polycythaemia vera (PV) versus healthy blood donors (NC) and patients with secondary polycythaemia (SP), we observed an altered CD4/CD8 ratio (p less than 0.01) mainly due to the decreased CD8 subpopulation in PV. We found an increased lymphocyte activity in PV patients when compared with both SP and NC: the interleukin 2 (IL-2) production was significantly higher (p less than 0.001) as was the lymphoproliferative response both to phytohaemagglutinin (p less than 0.001) and IL-2 (p less than 0.005). No significant differences were found between NC and SP. None of the PHA-stimulated PBMC samples from PV, SP or NC produced erythropoietin (EPO)-like or EPO-inhibitory activity. Our findings suggest an altered lymphoid lineage in PV patients.

Artefactual low lymphocyte activity caused by platelet contamination in the mononuclear cell preparations

Platelet (PLT) contamination in preparations of mononuclear cells (MNC) produces a significant decrease (P less than 0.02) in lymphoproliferative activity and interleukin 2 (IL2) production. This effect was observed in MNC preparations from either healthy blood donors or polyglobulic patients. In a dose-response curve carried out with increasing PLT number per MNC, progressive inhibition was found, reaching to 62.6% and 49.5%, respectively, to phytohemagglutinin and IL2 lymphoproliferative response and 87.8% in IL2 production, at 80 PLTs/MNC.