Refinement of the hereditary xerocytosis locus on chromosome 16q in a large Canadian kindred.

The hereditary stomatocytoses are a group of heterogeneous conditions associated with chronic red cell hemolysis for which the causative genetic mutations are not known. We investigated 137 members of a large Canadian kindred with phenotypic findings consistent with hereditary xerocytosis, one of the most common stomatocytosis syndromes. The objectives of this study were to characterize the clinical hallmarks of the hemolytic process, and to define the chromosomal region carrying the disease locus. The mode of inheritance was autosomal dominant. Affected family members had a well-compensated hemolysis, associated with an elevated MCHC, decreased osmotic fragility, decreased haptoglobin, and indirect hyperbilirubinemia. Cholelithiasis and progressive iron loading were common, despite normal hemoglobin levels. Quantitative erythrocyte morphologic evaluation revealed increased schistocytes, target cells, reticulocytes, and eccentrocytes in affected individuals; stomatocytes were not increased. Genetic linkage analysis confirmed the localization of the disease phenotype to chromosome 16q, and refined the candidate region to 16q24.2-16qter, a 2.4 million base pair interval containing 51 known or predicted genes.

Pulmonary arterial hypertension: the most devastating vascular complication of systemic sclerosis.

Pulmonary arterial hypertension (PAH) is a devastating vascular complication of a number of CTDs. In patients with SSc, PAH has a dramatic impact on prognosis and survival and is the single most common cause of disease-related death.Yearly echocardiographic screening for PAH is recommended in patients with SSc. If suspected, confirmation of PAH diagnosis by right heart catheterization is necessary. Treatment goals for patients with PAH associated with SSc (PAH-SSc) aim to slow disease progression and improve quality of life. Some measures used to gauge the effect of treatment in patients with PAH-SSc remain to be fully validated; the 6-min walk distance, for example, is a simple and reproducible means of assessing exercise capacity, but there exists a need to understand what constitutes a clinically relevant change in this specific patient population. Currently, pharmacological intervention in PAH-SSc may target one or more of three pathophysiological pathways in PAH. The prostacyclin analogue epoprostenol has been shown to improve exercise capacity and haemodynamics in PAH-SSc patients and similar data are available from smaller studies on trepostinil and iloprost. The dual endothelin receptor antagonist bosentan has been shown to improve exercise capacity and haemodynamics in PAH-SSc, and similar data have been obtained in small numbers of patients treated with the endothelin receptor A antagonists sitaxsentan and ambrisentan. Impaired production of nitric oxide may be addressed by inhibiting phosphodiesterase type-5 with sildenafil or possibly tadalafil. Combinations of multiple targeted therapies may be beneficial to this patient population.

Cardiac complications of systemic sclerosis.

The majority of patients with SSc are believed to have subclinical primary cardiac involvement. Overt cardiac manifestations of SSc are associated with poor prognosis and can be difficult to manage. Primary myocardial disease, i.e. without systemic or pulmonary hypertension and without significant pulmonary or renal disease, is postulated to be due to microvascular ischaemia. Undetected early cardiac manifestations can progress silently to myocardial fibrosis. Symptoms may manifest without warning and can rapidly lead to arrhythmia and left and right heart dysfunction and failure. Of the currently practical screening methods, annual echocardiography and/or evaluation of N-terminal portion of pro-B-type natriuretic peptide concentrations should therefore be employed in SSc patients, in order to anticipate the development of cardiac symptoms. Although there is limited evidence in respect of specific therapeutic options, treatment of early abnormalities with calcium channel blockers and angiotensin-converting enzyme inhibitors may improve myocardial perfusion and function, while standard management of overt cardiac disease is equally appropriate in the SSc population. However, it remains to be seen if early intervention can limit the progression of these life-threatening complications.

Screening for pulmonary arterial hypertension in systemic sclerosis.

The onset and progression of pulmonary arterial hypertension (PAH) in patients with systemic sclerosis (SSc) can be particularly aggressive; however, effective treatments are available. Therefore, early identification of patients with suspected PAH, confirmation of diagnosis, and intervention is essential. PAH may be challenging to diagnose in its earliest stages, particularly in populations that have multiple causes of breathlessness, and, therefore, screening is required. The optimal screening tools and methodology are, as yet, unknown, and this is confounded by a lack of consensus over which patients to screen. Current practice favours annual screening of all SSc patients using Doppler echocardiography to detect elevated right heart pressures. This will typically identify most patients with the various forms of pulmonary hypertension found in SSc. The optimum thresholds for Doppler echocardiography are still subject to investigation, especially for patients with mild pulmonary hypertension, and this technique may, therefore, yield a significant number of false-positives and a currently unknown number of false-negatives. Confirmatory right heart catheterisation remains necessary in all suspected cases. Further research is needed to identify the optimal tools and the screening approach with greatest specificity and selectivity.

Effects of enzyme replacement therapy on the cardiomyopathy of Anderson-Fabry disease: a randomised, double-blind, placebo-controlled clinical trial of agalsidase alfa.

BACKGROUND: Anderson-Fabry disease is an X-linked glycosphingolipid storage disorder caused by deficient activity of the lysosomal enzyme alpha-galactosidase A. This leads to a progressive accumulation of globotriaosylceramide (Gb(3)) in the lysosomes of cells throughout the body that ultimately results in premature death from renal, cardiac or cerebrovascular complications. Until recently, there was no effective therapy available for this disease. The present study was designed to assess the safety and efficacy of enzyme replacement therapy with agalsidase alfa on the cardiac manifestations of Anderson-Fabry disease. METHOD: The effects of therapy with agalsidase alfa on cardiac structure and function were assessed in a randomised, double-blind, placebo-controlled study of 15 adult male patients with Anderson-Fabry disease. The following parameters were measured at baseline and 6 months: left ventricular mass, QRS duration and levels of Gb(3) in cardiac tissue, urine sediment and plasma. After 6 months of the randomised trial patients were enrolled in a 2-year open-label extension study. RESULTS: Left ventricular mass, as measured by MRI, was significantly reduced following 6 months of treatment with agalsidase alfa compared with placebo (p = 0.041). A mean 20% reduction in myocardial Gb(3) content as assessed by serial transvenous endomyocardial biopsies was demonstrated over the 6 months of enzyme replacement compared to a mean 10% increase in patients receiving placebo (p = 0.42) CONCLUSION: Enzyme replacement therapy with agalsidase alfa resulted in regression of the hypertrophic cardiomyopathy associated with Anderson-Fabry disease.

Molecular basis of succinylcholine sensitivity in a prairie Hutterite kindred and genetic characterization of the region containing the BCHE gene.

The tetrameric glycoprotein butyrylcholinesterase (BChE; EC 3.1.1.8) is one of two enzymes that hydrolyze choline esters. The controlling gene (BCHE) is comprised of four coding exons and is located on chromosome 3q26. Based on BChE activity measurements in the presence and absence of dibucaine, usual (designated U) and atypical (designated A) gene products have been distinguished. Homozygotes for the A gene product are at risk for prolonged apnea following exposure to the surgical anesthetics succinylcholine or mivacurium. In this report, we detail biochemical and molecular investigations of succinylcholine sensitivity in a prairie Hutterite kindred. Our results establish that BChE activities in the family members are impacted by two distinct BCHE mutations, namely, c.209A>G p. D70G and c.1615G>A p. A539T. However, homozygotes for the c.209A>G mutation (i.e., atypical or A) are the only individuals whose BChE activity could lead to adverse reactions to succinylcholine. Interestingly, haplotype analysis of the chromosomal region containing BCHE indicates that the c.209A>G mutation is carried on a unique haplotype, suggesting that it was likely introduced into the population only once. Conversely, the c.1615G>A mutation is carried on various haplotypes and was likely introduced into the population more than once.

The Redelberger antigen: a family study, a family story.

The Redelberger antigen (Rba) was first discovered in 1974 on the RBCs of a blood donor who was an employee of the Community Blood Center in Dayton, Ohio. The discovery was made as a result of the investigation of a reagent contamination problem. Two examples of the Rba antigen were subsequently identified in the United Kingdom,but no "new"examples have been identified in the United States or Europe. Anti-Rba is a commonly occurring antibody, often found in combination with other antibody specificities, especially in combination with other antibodies to low-incidence antigens.

Consensus statement concerning cardiotoxicity occurring during haematopoietic stem cell transplantation in the treatment of autoimmune diseases, with special reference to systemic sclerosis and multiple sclerosis.

Autologous haematopoietic stem cell transplantation is now a feasible and effective treatment for selected patients with severe autoimmune diseases. Worldwide, over 650 patients have been transplanted in the context of phase I and II clinical trials. The results are encouraging enough to begin randomised phase III trials. However, as predicted, significant transplant-related morbidity and mortality have been observed. This is primarily due to complications related to either the stage of the disease at transplant or due to infections. The number of deaths related to cardiac toxicity is low. However, caution is required when cyclophosphamide or anthracyclines such as mitoxantrone are used in patients with a possible underlying heart damage, for example, systemic sclerosis patients. In November 2002, a meeting was held in Florence, bringing together a number of experts in various fields, including rheumatology, cardiology, neurology, pharmacology and transplantation medicine. The object of the meeting was to analyse existing data, both published or available, in the European Group for Blood and Marrow Transplantation autoimmune disease database, and to propose a safe approach to such patients. A full cardiological assessment before and during the transplant emerged as the major recommendation.

JAHK: a low frequency antigen associated with the rG complex of the Rh blood group system.

We have investigated a 'new' low frequency antigen JAHK, which is a marker for the rare Rh gene complex rG. The rG haplotype does not produce any D, c or E antigens, but does produce a strong G antigen. The rG haplotype [d(C)(e)G] is associated with weak C and weak e antigens. Three unrelated rG/dce individuals and one rG/rG propositus were JAHK+. In addition, three propositi whose red cells had a typical expression of C and/or e antigen, which could not be shown to be rG because of a normal D antigen produced by the haplotype in trans, were also JAHK+. Families of three of the propositi demonstrate the inheritance of JAHK as a Mendelian dominant character. It is likely that the JAHK antigen results from conformational changes in an RhCcEe protein that has the amino acid characteristic of c antigen at position 16 and the amino acid residues characteristic of C antigen at positions 60, 68, and 103. JAHK has been assigned the number RH53.

Incorporation of fatty acids into phosphatidylcholine is reduced during storage of human erythrocytes: evidence for distinct lysophosphatidylcholine acyltransferases.

The incorporation of [1-14C]palmitic or [1-14C]oleic acid into phosphatidylcholine and the effect on blood group antigen expression were examined in human erythrocytes stored at 4 degrees C for 0-3 weeks. Blood drawn into EDTA was obtained by venepuncture from healthy volunteers. A 50% suspension of washed erythrocytes was incubated in buffer containing [1-14C]fatty acid for up to 60 min at 37 degrees C with moderate shaking. Phosphatidylcholine was extracted and analyzed for uptake of radiolabelled fatty acid and phospholipid phosphorus content. Incorporation of [1-14C]palmitic or [1-14C]oleic acid into phosphatidylcholine was reduced during storage. The mechanism for the reduction in radiolabelled fatty acid incorporation into phosphatidylcholine was a 64% (p < 0.05) reduction in membrane phospholipase A2 activity. Although human erythrocyte membranes isolated from freshly drawn blood are capable of reacylating lysophosphatidylcholine to phosphatidylcholine, with storage, a markedly different substrate preference between palmitoyl-Coenzyme A and oleoyl-Coenzyme A was observed. Lysophosphatidylcholine acyltransferase activity assayed with oleoyl-Coenzyme A was unaltered with storage. In contrast, lysophosphatidylcholine acyltransferase activity assayed with palmitoyl-Coenzyme A was elevated 5.5-fold (p < 0.05). Despite these changes, storage of erythrocytes for up to 3 weeks did not result in altered expression of the various blood group antigens investigated. We conclude that the incorporation of palmitate and oleate into phosphatidylcholine is dramatically reduced during storage of human erythrocytes. The observed differential in vitro substrate utilization suggests that distinct acyltransferases are involved in the acylation of lysophosphatidylcholine to phosphatidylcholine in human erythrocytes.

An amino acid substitution in the putative second extracellular loop of RBC band 3 accounts for the Froese blood group polymorphism.

BACKGROUND: The low incidence RBC antigen Fr(a) has been excluded from 17 of the 25 established blood group systems. Previous genetic analysis assigned the gene controlling Fr(a) expression to the same chromosomal region as the solute carrier family 4, anion exchanger member 1 gene (SLC4A1). Because SLC4A1 encodes RBC band 3 and controls the expression of Diego blood group system antigens, the possible relationship of Fr(a) to the Diego blood group system was investigated by molecular analysis of SLC4A1. STUDY DESIGN AND METHODS: Blood samples were obtained from the members of two unrelated Mennonite kindreds segregating for Fr(a). DNA was extracted, amplified by PCR using intronic primer sets flanking exons 11-20 of SLC4A1, and screened by single-strand conformation polymorphism (SSCP) analysis. Those exons displaying SSCPs were subjected to DNA sequence analysis. RESULTS: An exon 13 SSCP mobility shift was observed in the DNA from all Fr(a+) persons that was not seen in the DNA from Fr(a-) family members or control subjects. Linkage between the exon 13 SSCP and FR:(a) was established, with peak lods = 3.62 at theta = 0.00 for combined paternal and maternal meioses. DNA sequencing revealed a GAG --> AAG mutation that underlies a Glu480Lys substitution in RBC band 3. CONCLUSIONS: A point mutation in exon 13 of SLC4A1 accounting for a Glu480Lys substitution in band 3 controls Fr(a) expression. On the basis of these our results, the International Society of Blood Transfusion Working Party on Terminology for Red Cell Surface Antigens has assigned Fr(a) to the Diego blood group system, with the designation DI20.

Confirmation of the assignment of the Dombrock blood group locus (DO) to chromosome 12p: narrowing the boundaries to 12p12.3-p13.2.

BACKGROUND AND OBJECTIVES: Antigens belonging to the Dombrock blood group system have been well characterized serologically. Despite being reasonably polymorphic, chromosomal localization of the gene controlling Dombrock expression (DO) has proved difficult. In the past, DO had been provisionally assigned to chromosomes 1 and 4; more recently, DO was provisionally assigned to chromosome 12. The current study was undertaken in an attempt to confirm or refute this latest assignment. MATERIALS AND METHODS: DNA from a series of families segregating for DO was amplified by polymerase chain reaction and analyzed for trinucleotide or tetranucleotide repeat polymorphisms of four anonymous DNA markers (D12S1042, D12S373, D12S391, D12S372) and of the von Willebrand factor gene (VWF). Lods for or against linkage were determined between DO and each marker. RESULTS: DO is linked to all five markers. The closest linkage was established between DO and D12S373, and DO and D12S391, with peak lods for combined paternal and maternal meioses of 7.16 at peak recombination fraction (theta) = 0.08 and 7.69 at theta = 0.08, respectively. CONCLUSIONS: We have confirmed the assignment of the Dombrock blood group locus to chromosome 12p and have refined its regional localization to 12p12.3-p13.2.

The MNS blood group antigens, Vr (MNS12) and Mt(a) (MNS14), each arise from an amino acid substitution on glycophorin A.

BACKGROUND AND OBJECTIVES: The antigens, Vr (MNS12) and Mt(a) (MNS14), are low-incidence antigens of the MNS blood group system. The Vr antigen has been found only on the red blood cells (RBCs) of persons of Dutch ancestry whereas the Mt(a) antigen has been found on the RBCs of persons from a wide geographic distribution. The objective of this study was to determine the molecular basis of Vr and Mt(a). MATERIALS AND METHODS: Following RT-PCR amplification of total RNA isolated from one Vr+ person (G488) and one Mt(a+) person (GH), the genes encoding glycophorin A (GYPA) and glycophorin B (GYPB) were cloned and sequenced. To confirm the point mutation observed in the cDNA from G488 (Vr+), GYPA exon 3 was cloned and sequenced from the genomic DNA of G488 and a second unrelated Vr+ person (MU). A restriction fragment length polymorphism (RFLP) assay was used to analyze genomic DNA from 11 Mt(a+) persons (10 unrelated) following PCR amplification of GYPA exon 3. RESULTS: The coding sequence of GYPB was normal in both G488 (Vr+) and GH (Mt(a+)). Sequencing data from GYPA clones derived from G488 showed to full length GYPA sequences: A normal GYPA M allele and a GYPA M allele with a point mutation 197C-->A. Sequencing of GYPA exon 3 from G488 and MU confirmed the point mutation. Sequencing data drom GYPA clones derived from GH showed two full length GYPA sequences: a normal GYPA M allele and a GYPA N allele with a point mutation 230C-->T. RFLP analysis based on the point mutation showed that DNA from 11 Mt(a+) samples were heterozygous for the point mutation. CONCLUSION: The Vr antigen arises from a point mutation 197C-->A on GYPA which is predicted to change serine at position 47 to tyrosine. This change introduces a new alpha-chymotrypsin cleavage site. The Mt(a) antigen arises from a point mutation 230C-->T which is predicted to change threonine at position 58 to isoleucine.

Amino acid substitutions in human erythroid protein band 3 account for the low-incidence antigens NFLD and BOW.

BACKGROUND: The low-incidence red cell antigens NFLD (700.37) and BOW (700.46) were first described in 1984 and 1988, respectively. Recent investigations showed that antigens of the Diego blood group system (including a number of low-incidence antigens) are coded by SLC4A1 (solute carrier family 4, anion exchanger member 1 gene). Among these newly characterized Diego system antigens is Wu (designated DI9). Because a serologic relationship among Wu, NFLD, and BOW has been established, a series of genetic and molecular investigations of SLC4A1 in relation to NFLD and BOW were undertaken. STUDY DESIGN AND METHODS: By the use of exon-specific primers, single-strand conformational polymorphism (SSCP) analysis of SLC4A1 was performed on DNA isolated from an NFLD+ person from Japan, from the members of a Canadian kindred segregating for NFLD, and from two unrelated BOW+ persons. Exons displaying SSCPs were subjected to genetic linkage analysis (for NFLD only) and DNA sequencing. RESULTS: SSCPs in DNA amplified from exons 12 and 14 of SLC4A1 were observed for all NFLD+ subjects. Linkage between each of these polymorphisms and NFLD was established with peak lods = 4.82 at theta = 0.00 for combined paternal and maternal meiosis. DNA sequencing of exons 12 and 14 of SLC4A1 from NFLD+ persons identified A-->T and C-->G mutations that underlie Glu429Asp and Pro561Ala substitutions in human erythroid band 3 protein (band 3). DNA from the two unrelated BOW+ persons only exhibited an SSCP in exon 14 of SLC4A1. Subsequent DNA sequencing revealed a C-->T mutation that accounts for a Pro561Ser substitution in band 3. CONCLUSION: SLC4A1 codes for the low-incidence red cell antigens NFLD and BOW. In light of these findings, both antigens have been assigned to the Diego blood group system.

Distinctive Swann blood group genotypes: molecular investigations.

BACKGROUND AND OBJECTIVES: Phenotypically, Sw(a+) erythrocytes have been classified as either 700:4,41 or 700:4,-41. Since anti-700.4, in particular, and sometimes anti-700.41 are contained in reagents defining other low-incidence antigens that are members of the Diego blood group system, we undertook the current investigation in an attempt to establish whether or not Swann antigens are also Diego system members. MATERIALS AND METHODS: DNA from the members of three unrelated kindreds whose red cells type as Sw(a+) was isolated and analyzed for variation in SLC4A1 (solute carrier family, anion exchanger member 1 gene) by single-strand conformational polymorphism (SSCP) and DNA sequence analyses. RESULTS: Polymerase chain reaction-amplified exon 16 SLC4A1 products from the DNA of all Sw(a+) individuals displayed a mobility shift by SSCP. A similar mobility shift was not observed in the DNA from Sw(a-) family members or in the amplified DNA from control individuals. DNA sequencing revealed different mutations, CGG-->CAG and CGG-->TGG, that result in Arg646Gln and Arg646Trp substitutions in erythroid protein band 3, respectively. CONCLUSION: Through genotypic analyses, we have characterized two point mutations related to the Swann blood group. The possible relationship between the resultant amino acid substitutions and the expression of Swann antigens has been discussed.

Helicobacter pylori in the Canadian arctic: seroprevalence and detection in community water samples.

OBJECTIVE: Many North American arctic communities are characterized by risk markers associated with Helicobacter pylori (H. pylori) infection, including overcrowded housing and inadequate water supply and sanitation systems. Our aim was to determine the seroprevalence of H. pylori infection in two traditional Inuit communities in the central Canadian arctic and to test for the presence of H. pylori, by polymerase chain reaction (PCR), in local water supplies. METHODS: Samples of venous whole blood from adults and capillary blood from children were collected and analyzed by enzyme immunoassay and Helisal Rapid Test, respectively, for IgG antibody to H. pylori. Antibodies to CagA were detected by enzyme immunoassay, and ABO and Lewis antigens were also determined. Demographic and clinical information were collected by questionnaire. Water samples from each community were tested for H. pylori by PCR. RESULTS: One hundred-thirty (50.8%) of 256 subjects from the two communities were positive for H. pylori IgG antibodies. Seropositive subjects were more likely to be male, compared with seronegative individuals (p = 0.01). Antibody status did not differ with respect to age, community, alcohol or cigarette use, number of persons per household, gastrointestinal complaints or previous investigations, medications, or presence of blood group O, Lewis a-b+. CagA antibodies were detected in 78 (61.9%) of 126 H. pylori-seropositive subjects tested; however, 41 (35.3%) of 116 H. pylori-seronegative subjects were also CagA positive. Water samples taken from the water delivery truck in Chesterfield Inlet and two lakes near Repulse Bay were positive for H. pylori. CONCLUSION: The seroprevalence of H. pylori in the study group was higher than rates in southern Canadian populations, but lower than the seroprevalence previously documented in a Canadian subarctic Indian (First Nations) community. The detection of H. pylori in local water supplies may indicate a natural reservoir for the organism or possible contamination from human sewage.

Seroprevalence of Helicobacter pylori, incidence of gastric cancer, and peptic ulcer-associated hospitalizations in a Canadian Indian population.

The living conditions of many aboriginal communities in Canada may place their residents at risk for H. pylori infection. Our aims were to determine: (1) the seroprevalence of H. pylori in a traditional Indian community, (2) the clinical relevance of H. pylori infection in this population, and (3) if H. pylori could be identified by polymerase chain reaction from the local water. A demographic questionnaire was administered, and blood was collected from subjects in an Indian community in northwestern Manitoba. The serum was analyzed by ELISA for IgG to H. pylori and to CagA. ABO and Lewis antigens were tested. Age-adjusted incidence of gastric cancer and of hospitalizations associated with diagnoses of peptic ulcer were determined for the Indian and non-Indian Manitoba population in the years 1989-1993. Nested PCR was performed on lake water using H. pylori-specific primers and the amplicons probed with an internal Dig-labeled probe. Three hundred six (59%) of approximately 518 individuals who were resident in the community at the time of the study were enrolled. The ELISA for H. pylori was positive in 291 (95%). There was no association between H. pylori seropositivity and age, sex, gastrointestinal complaints, medications, housing characteristics, and ABO or Lewis antigen status. CagA was positive in 84.5% of infected subjects. The average annual age-adjusted incidence of hospitalizations associated with diagnoses of peptic ulcer disease in Manitoba was higher for treaty-status Indians (394.3/100,000) than for non-Indians (203.8/100,000), but gastric cancer rates were similar (11.2/100,000 vs 11.6/100,000). No H. pylori DNA was detected in the lake water. In conclusion, the seroprevalence of CagA-positive H. pylori is high in this representative Manitoban Indian community. This may be associated with an increased risk for peptic ulcer disease but is not associated with an increased risk for gastric cancer.

Two examples of an inseparable antibody that reacts equally well with DW+ and Rh32+ red blood cells.

BACKGROUND AND OBJECTIVES: Anti-DW is a rare specificity that detects an antigen on DVa red blood cells (RBCs). Some anti-DW contain an inseparable component that cross-reacts weakly with RBCs expressing the low-incidence Rh antigen Rh32. RH32 is expressed by RBCs with either the R=Nor the DBT phenotype. CASE REPORT: We describe here an antibody found in the serum of 2 patients that reacts equally well with RBCs possessing either DVa, R=N, or DBT phenotypes. The reactivity for DW and Rh32 antigens could not be separated by adsorption onto and elution from DW+Rh32- or from DW-Rh32+ RBCs. CONCLUSIONS: We suggest that amino acids encoded by nucleotides at the junction of exon 4 of RHD to exon 5 of RHCE may induce a conformation that is recognized by these equally reactive inseparable antibodies. Until such time that the epitope recognized by these antibodies is defined, we recommend use of the descriptive name anti-DW/Rh32.

The ELO blood group polymorphism is located in the putative first extracellular loop of human erythrocyte band 3.

BACKGROUND AND OBJECTIVES: The low incidence red cell antigen ELO (700.51) has been excluded from 13 of 23 established blood group systems. Information relative to the Diego system has not been reported. To investigate a possible association between ELO and the gene controlling Diego blood group polymorphisms, we undertook molecular studies of AE1 (anion exchanger 1 gene). MATERIALS AND METHODS: DNA from a family segregating for ELO and from the original ELO proposita was amplified by PCR using intronic primers flanking exons 11-20 of AE1. Subsequently, single-strand conformational polymorphism (SSCP) analysis and DNA sequencing were conducted. RESULTS: We have observed an exon 12 SSCP in all ELO+ individuals tested. This SSCP is the result of a C-->T mutation in exon 12 of AE1 which leads to an Arg432-->Trp amino acid substitution in the putative first extracellular loop of band 3 and thereby accounts for the Diego blood group system polymorphism known as ELO. CONCLUSIONS: In light of these findings, the International Society of Blood Transfusion Working Party on Terminology for Red Cell Surface Antigens has designated ELO as a member of the Diego blood group system (010008 or D18) and rendered the previous numerical designation (700.51) obsolete.