Simple Heterozygotes Research Articles

Unraveling thalassemia intermedia: Novel insights of a hemoglobin Jax [HBA2:c.44G>C] and deletional α0-thalassemia interaction phenotype.

To elucidate the molecular basis, hematological features, and electrophoretic and chromatographic mobility behavior of an unstable α2-globin chain variant, and to describe the diagnostic approach. A Thai patient with unexplained chronic anemia and her daughter were investigated. Hematological data were analyzed using a standard automated cell counter. Hemoglobin was analyzed using high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). Mutational analysis was performed using appropriate polymerase chain reaction (PCR) techniques and direct sequencing. Additionally, α-globin haplotype analysis was conducted. Simple and rapid diagnostic methods were developed. Hemoglobin analysis in the patient revealed anomalous peaks separated from normal hemoglobin visible using the HPLC technique. These peaks were virtually absent in the daughter. DNA analysis identified a G to C mutation at codon 14 of the α2-globin gene responsible for hemoglobin Jax in trans to the α0-thalassemia gene in the patient. Heterozygosity of this mutation was identified in her daughter. Hematological analysis showed mild thalassemia-like changes in simple heterozygotes and exhibited a hemoglobin H-like phenotype when combined with α0-thalassemia. Isopropanol stability testing and bioinformatic software indicated that the variant was unstable and potentially damaging. This mutation was confirmed using allele-specific PCR. Hemoglobin Jax was strongly associated with the haplotype [+ - S + - + -]. Hemoglobin Jax, a pathological α-globin variant, is asymptomatic in simple heterozygotes and demonstrates more pronounced clinical effects when associated with deletional α-thalassemia. This knowledge can help develop strategies to prevent hemoglobinopathies in regions of high prevalence. Accurate identification requires DNA level analysis.

A clinical update of compound heterozygosity for hemoglobin Hekinan II [a27(B8)Glu-Asp; HBA1: c.84G>T] variant in China.

Hemoglobin (Hb) Hekinan II (A27; Glu-Asp) is an α-chain variant, and its interaction with the common Southeast Asian (--SEA/) α-thalassemia (α-thal) deletion is rarely reported. This study provides a clinical update of Hb Hekinan II associated with (--SEA/) α-thal. A total of 11 simple heterozygotes and 20 composite heterozygotes for Hb Hekinan II and (--SEA/) α-thal were included based on molecular diagnosis. Hb Hekinan II exhibited a significant increase in hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin content, but a decrease in red blood cell level compared with α+ thalassemia deletion. Compared with (--SEA/) α-thal, composite heterozygotes for Hb Hekinan II and (--SEA/) α-thal showed similar erythrocyte parameters. Both heterozygotes with and without (--SEA/) α-thal showed low Hb A2 level. Hb Hekinan II showed abnormal performance in high-performance liquid chromatography but not in capillary electrophoresis. Hb Hekinan II is a benign Hb variant. The heterozygotes exhibit clinically asymptomatic coinheritance with (--SEA/) α-thal having comparable hematological phenotype to simple (--SEA/) α-thal. The combination of hematological and molecular analysis helped to improve the detection rate of this rare variant.

Frameshift coding sequence variants in the LPL gene: identification of two novel events and exploration of the genotype–phenotype relationship for variants reported to date

BackgroundLipoprotein lipase (LPL) is the rate-limiting enzyme for triglyceride hydrolysis. Homozygous or compound heterozygous LPL variants cause autosomal recessive familial chylomicronemia syndrome (FCS), whereas simple heterozygous LPL variants are associated with hypertriglyceridemia (HTG) and HTG-related disorders. LPL frameshift coding sequence variants usually cause complete functional loss of the affected allele, thereby allowing exploration of the impact of different levels of LPL function in human disease.MethodsAll exons and flanking intronic regions of LPL were Sanger sequenced in patients with HTG-related acute pancreatitis (HTG-AP) or HTG-AP in pregnancy. Previously reported LPL frameshift coding sequence variants were collated from the Human Gene Mutation Database and through PubMed keyword searching. Original reports were manually evaluated for the following information: zygosity status of the variant, plasma LPL activity of the variant carrier, disease referred for genetic analysis, patient’s age at genetic analysis, and patient’s disease history. SpliceAI was employed to predict the potential impact of collated variants on splicing.ResultsTwo novel rare variants were identified, and 53 known LPL frameshift coding sequence variants were collated. Of the 51 variants informative for zygosity, 30 were simple heterozygotes, 12 were homozygotes, and 9 were compound heterozygotes. Careful evaluation of the 55 variants with respect to their clinical and genetic data generated several interesting findings. First, we conclude that 6–7% residual LPL function could significantly delay the age of onset of FCS and reduce the prevalence of FCS-associated syndromes. Second, whereas a large majority of LPL frameshift coding sequence variants completely disrupt gene function through their "frameshift" nature, a small fraction of these variants may act wholly or partly as "in-frame" variants, leading to the generation of protein products with some residual LPL function. Third, we identified two candidate LPL frameshift coding sequence variants that may retain residual function based on genotype–phenotype correlation or SpliceAI-predicted data.ConclusionsThis study reported two novel LPL variants and yielded new insights into the genotype–phenotype relationship as it pertains to LPL frameshift coding sequence variants.

Chromosome Asynapsis Is the Main Cause of Male Sterility in the Interspecies Hybrids of East Asian Voles (Alexandromys, Rodentia, Arvicolinae).

Closely related mammalian species often have differences in chromosome number and morphology, but there is still a debate about how these differences relate to reproductive isolation. To study the role of chromosome rearrangements in speciation, we used the gray voles in the Alexandromys genus as a model. These voles have a high level of chromosome polymorphism and substantial karyotypic divergence. We investigated testis histology and meiotic chromosome behavior in the captive-bred colonies of Alexandromys maximowiczii, Alexandromys mujanensis, two chromosome races of Alexandromys evoronensis, and their interracial and interspecies hybrids, to explore the relationship between karyotypic differences and male hybrid sterility. We found that the seminiferous tubules of the males of the parental species and the interracial hybrids, which were simple heterozygotes for one or more chromosome rearrangements, contained germ cells at all stages of spermatogenesis, indicating their potential fertility. Their meiotic cells displayed orderly chromosome synapsis and recombination. In contrast, all interspecies male hybrids, which were complex heterozygotes for a series of chromosome rearrangements, showed signs of complete sterility. Their spermatogenesis was mainly arrested at the zygotene- or pachytene-like stages due to the formation of complex multivalent chains, which caused extended chromosome asynapsis. The asynapsis led to the silencing of unsynapsed chromatin. We suggest that chromosome asynapsis is the main cause of meiotic arrest and male sterility in the interspecies hybrids of East Asian voles.

Phenotypes of Granular Corneal Dystrophy Type 2 among Koreans in Their Twenties

Purpose: Granular corneal dystrophy type 2 (GCD2) is a hereditary disease that features granular and lattice stromal deposits in the cornea. There are homozygotes and heterozygotes and the opacities are exacerbated by corneal trauma or surgery, such as laser in situ keratomileusis (LASIK). As there is individual variability in GCD2 phenotypes, we investigated various corneal features of GCD2 patients in their twenties, the main age group for refractive surgery.Methods: From genetically confirmed GCD2 patients who had an R124H mutation of the transforming growth factor β induced (<i>TGFBI</i>) gene at age 20 to 29 years, we chose representative patients: one homozygote; one compound heterozygote; one simple heterozygote with a severe phenotype with many granular deposits; one common heterozygote; and four heterozygotes with normal corneas. The corneas of all patients were subject to slit-lamp examination and photographed.Results: The homozygote had confluent granular deposits covering the cornea. The compound heterozygote had granular and lattice deposits covering the center of the cornea. The patient with a severe phenotype had more than 30 granular deposits in one eye, but was a simple GCD2 heterozygote, verified by full-sequencing of the <i>TGFBI</i> gene. In the four patients with normal corneas, a single small lesion was subsequently detected during follow-up in two, at 3 weeks and 6 months, respectively. Both corneas were judged clear at chance examinations.Conclusions: Among Koreans in their twenties, GCD2 patients have various phenotypes, from clear corneas to severe confluent opacities. There are GCD2 heterozygotes with nearly clear corneas, so caution must be taken when choosing patients for refractive surgery.

Molecular characterisation of Hb Akron [β52 (D3) Asp→Val] combined with thalassaemia in a Chinese family

AimsHb Akron (HBB:c.158A>T) is a rare β-chain variant and many characteristics about its clinical features still remain unclear. In this study, we aimed to explore the molecular and haematological characterisations...

Genotypic and hematological characteristics of 83 β-thalassemia mutation carriers and patients from Henan Province

To investigate the genotypic and hematological characteristics of β-thalassemia patients and carriers from Henan Province of China. Clinical data of the patients and carriers were collected. Results of routine blood test, hemoglobin electrophoresis and genetic testing were retrospectively analyzed. Of the 83 β-thalassemia patients and carriers, there were 46 females and 37 males, and their mean age was 27.37 ± 14.71, ranging from 5 months to 83 years. A total of 13 types of β-thalassemia alleles (86 alleles in total) were detected, with the most common three including ISV-II-654(C>T) (33.72%), CD41-42(-TTCT) (26.74%) and CD17(A>T) (18.60%). Five rare alleles, including CD8-9(+G), IVS-II-1(G>A), CD42(T>G), and start codons ATG>AGG and ATG>ACG were identified. Among these, HBB: c.128T>G(CD42T>G) was previously unreported in China. Fifteen β-thalassemia genotypes were detected, which included 12 simple heterozygote genotypes (80 cases, 96.40%), 2 double heterozygote genotypes (2 cases, 2.40%) and 1 homozygote genotype (1 case, 1.20%). The main manifestations were mild microcytic hypochromic anemia and raised HbA2. Compared with those with a β+/βN genotype, carriers with a β0/βN genotype have lower mean corpuscular volume (MCV) and mean corpusular hemoglobin (MCH) but higher HbA2 (P<0.05). β-thalassemia is not rare in Henan Province and its characteristics are different from those in high incidence areas, which deserves close attention. The newly discovered HBB: c.128T>G (CD42T>G) has enriched the spectrum of β-thalassemia mutations in China. Above results will also facilitate genetic counseling and prenatal diagnosis of β-thalassemia in Henan Province.

Hemochromatosis, alcoholism and unhealthy dietary fat: a case report

BackgroundHereditary hemochromatosis is an autosomal recessive disorder where the clinical phenotype of skin pigmentation and organ damage occurs only in homozygotes. Simple heterozygotes, that is, just C282Y, typically do not develop iron overload. Here we present a case where a simple heterozygote in combination with alcoholism developed high ferritin and high transferrin saturation levels indicative of iron overload. Though alcoholism alone could explain her presentation, we hypothesize that an inflammatory cocktail of iron and alcohol probably caused our patient to succumb to acute liver failure at a very young age.Case presentationA 29-year-old Caucasian woman presented to the hospital with progressively worsening yellowish discoloration of her eyes and skin associated with anorexia, nausea, vomiting, diffuse abdominal discomfort, increasing abdominal girth, dark urine and pale stools for about 2 weeks. Family history was significant for hereditary hemochromatosis. Her father was a simple heterozygote and her grandmother was homozygous for C282Y. Physical examination showed scleral icterus, distended abdomen with hepatomegaly and mild generalized tenderness. Lab test results showed an elevated white blood cell count, ferritin 539 ng/dL, transferrin saturation 58.23%, elevated liver enzymes, elevated international normalized ratio (INR), low albumin, Alcoholic Liver Disease/Nonalcoholic Fatty Liver Disease (ALD/NAFLD) Index (ANI) of 2.6, suggesting a 93.2% probability of alcoholic liver disease, and phosphatidyl ethanol level of 537ng/ml. Genetic testing showed that the patient was heterozygous for human homeostatic iron regulator protein (HFE) C282Y mutation and the normal allele. Computed tomography (CT) of the abdomen revealed hepatomegaly, portal hypertension and generalized anasarca. Magnetic resonance cholangiopancreatography (MRCP) showed negative results for bile duct pathology. Workup for other causes of liver disease was negative. A diagnosis of acute alcoholic hepatitis was made, with Maddrey’s discriminant function of > 32, so prednisolone was started. Her bilirubin and INR continued to increase despite steroids, and the patient unfortunately died.ConclusionOur case highlights the importance of considering hemochromatosis in the differential diagnosis of young patients presenting with liver failure, including cases suggestive of alcoholism as the likely etiology. Larger studies are needed to investigate the role of non-iron factors like alcohol and viral hepatitis in the progression of liver disease in simple heterozygotes with hereditary hemochromatosis, given the high prevalence of this mutation in persons of Northern European descent.

The Genetic Perspective of Familial Glucocorticoid Deficiency: In Silico Analysis of Two Novel Variants.

Familial glucocorticoid deficiency is a rare autosomal recessive genetic disorder which belongs to a group of primary adrenal insufficiency (PAI) and is mainly caused by mutations in the MC2R and MRAP genes. A comprehensive search was conducted to find the reported variants of MC2R and MRAP genes. In silico pathogenic analysis was performed for the reported variants. PCR amplification and sequencing were performed for three patients. Structural analysis, modeling, and interactome analysis were applied to characterize novel MC2R variants and their proteins. About 80% of MC2R-related cases showed the clinical symptoms which were diagnosed at <2 years old. 107 patients had MC2R mutations (85 homozygotes, 21 compound heterozygotes, and 1 simple heterozygote). 59 variants were found in the MC2R gene. Four mutations were responsible for half of patients. 39 homozygous patients had MRAP mutations; 14 variants were determined in the MRAP gene. Nine proteins were predicted by STRING to associate with the studied proteins. Two novel MC2R variants, c.128T > G (p.Leu43Arg) and c.251T > A (p.Ile84Asn), were found in two patients at the age of above and below 2 years, respectively. Mutations in MC2R and MRAP genes are the main cause of FGD. Genetic studies and in silico analysis will help to confirm the diagnosis.

Hematological Characteristics of β-Globin Gene Mutation –50 (G>A) (HBB: c.-100G>A) Carriers in Mainland China

The −50 (G>A) (HBB: c.-100G>A) mutation was first reported as a β-thalassemia (β-thal) allele in a Chinese family. However, the hematological features of carriers with this variant are not available. In this study, we present the hematological data associated with −50 (G>A) to determine its phenotype. During a 4-year period, eight simple heterozygotes and three double heterozygotes for the −50 mutation and α-thalassemia (α-thal) were included. The simple heterozygotes had normal hematological parameters. The double heterozygotes had the hematological findings of simple α-thal heterozygotes. Two subjects with a compound heterozygosity for −50 and β-thal were also found, and both had typical hematological parameters of β-thal trait. Therefore, we present evidence that −50 (G>A) is likely a silent β-thal allele. Compound heterozygotes for −50/β-thal had no phenotype of severe β-thal. This information might be helpful in genetic counseling for couples in thalassemia high-prevalence areas.

Interactions of unstable hemoglobin Rush with thalassemia and hemoglobin E result in thalassemia intermedia

ABSTRACTBackground: The clinical consequences and significance of many unstable hemoglobins interacting with other hemoglobinopathies remain unrecognized. Here we first explore molecular and hematological characterizations of previously undescribed compound heterozygosity states for unstable hemoglobin Rush (Hb Rush, Beta 101 Glu > Gln, HBB:c.304G > C) with Hb E and different forms of thalassemia.Methods: Hematological assays, globin gene mutation assays and β-globin gene cluster haplotype were conducted in 11 patients from 8 unrelated Chinese ethnic families with unexplained hemoglobin separation fraction in hemoglobin gel electrophoresis.Results: Hb Rush in various combinations with Hb E, β0-thalassemias and α+-thalassemia were identified. Hb Rush simple heterozygote was generally associated with mild hemolytic anemia, and the compound heterozygotes of Hb Rush and the other β-globin variants led to thalassemia intermedia phenotypes with moderate anemia. Hemoglobin electrophoreses showed that the co-presence of Hb Rush with either Hb E or β0-thalassemias increased proportion of Hb Rush due to relative decrease of other globin chain synthesis. Beta-globin gene cluster haplotype analysis suggested a common origin of the Hb Rush variant in the Chinese families of different ethnic ancestry.Conclusions: Unstable Hb Rush interacting with β-thalassemia result in thalassemia intermedia phenotypes, which demonstrated the clinical significance of Hb Rush and new insights into complex mechanism of clinical heterogeneity of thalassemia.

Identification of ten novel SLC5A2 mutations and determination of the renal threshold for glucose excretion in Chinese patients with familial renal glucosuria

Identification of ten novel SLC5A2 mutations and determination of the renal threshold for glucose excretion in Chinese patients with familial renal glucosuria

Thalassemia major phenotype caused by HB Zürich-Albisrieden [α2 59(E8) Gly &gt; Arg (HBA2:C.178G &gt; C)] in a Brazilian child

Hemoglobin (Hb) Zürich-Albisrieden (ZA) [α2 59(E8) Gly>Arg; HBA2:c.178G>C] is a rare and highly unstable α-chain variant. A few simple and compound heterozygotes (αZA α/αα and -/αZA α, respectively) have been described so far in Switzerland and China. We describe here a case of homozygosity for the Hb ZA mutation (αZA α/αZA α) in a Brazilian child with severe congenital hemolytic anemia and ineffective erythropoiesis.

Chromosome Synapsis and Recombination in Male Hybrids between Two Chromosome Races of the Common Shrew (Sorex araneus L., Soricidae, Eulipotyphla).

Hybrid zones between chromosome races of the common shrew (Sorex araneus) provide exceptional models to study the potential role of chromosome rearrangements in the initial steps of speciation. The Novosibirsk and Tomsk races differ by a series of Robertsonian fusions with monobrachial homology. They form a narrow hybrid zone and generate hybrids with both simple (chain of three chromosomes) and complex (chain of eight or nine) synaptic configurations. Using immunolocalisation of the meiotic proteins, we examined chromosome pairing and recombination in males from the hybrid zone. Homozygotes and simple heterozygotes for Robertsonian fusions showed a low frequency of synaptic aberrations (<10%). The carriers of complex synaptic configurations showed multiple pairing abnormalities, which might lead to reduced fertility. The recombination frequency in the proximal regions of most chromosomes of all karyotypes was much lower than in the other regions. The strong suppression of recombination in the pericentromeric regions and co-segregation of race specific chromosomes involved in the long chains would be expected to lead to linkage disequilibrium between genes located there. Genic differentiation, together with the high frequency of pairing aberrations in male carriers of the long chains, might contribute to maintenance of the narrow hybrid zone.

Impact of rare variants in autosomal dominant hypercholesterolemia causing genes.

The systematic analysis of the major candidate genes in autosomal dominant hypercholesterolemia (ADH) and the use of next-generation sequencing (NGS) technology have made possible the discovery of several rare gene variants whose pathogenic effect in most cases remains poorly defined. One major advance in the field has been the adoption of a set of international guidelines for the assignment of pathogenicity to low-density lipoprotein receptor (LDLR) gene variants based on the use of softwares, complemented with data available from literature and public databases. The clinical impact of several novel rare variants in LDLR, APOB, PCSK9, APOE genes have been reported in large studies describing patients with ADH found to be homozygotes/compound heterozygotes, double heterozygotes, or simple heterozygotes. In-vitro functional studies have been conducted to clarify the effect of some rare ApoB variants on LDL binding to LDLR and the impact of a rare ApoE variant on the uptake of VLDL and LDL by hepatocytes. The update of the ADH gene variants database and the classification of variants in categories of pathogenicity is a major advance in the understanding the pathophysiology of ADH and in the management of this disorder. The studies of molecularly characterized patients with ADH have emphasized the impact of a specific variant and the variable clinical expression of different genotypes. The functional studies of some variants have increased our understanding of the molecular bases of some forms of ADH.

HFE p.C282Y homozygosity predisposes to rapid serum ferritin rise after menopause: A genotype-stratified cohort study of hemochromatosis in Australian women.

Women who are homozygous for the p.C282Y mutation in the HFE gene are at much lower risk of iron overload-related disease than p.C282Y homozygous men, presumably because of the iron-depleting effects of menstruation and pregnancy. We used data from a population cohort study to model the impact of menstruation cessation at menopause on serum ferritin (SF) levels in female p.C282Y homozygotes, with p.C282Y/p.H63D simple or compound heterozygotes and those with neither p.C282Y nor p.H63D mutations (HFE wild types) as comparison groups. A sample of the Melbourne Collaborative Cohort Study was selected for the "HealthIron" study (n=1438) including all HFE p.C282Y homozygotes plus a random sample stratified by HFE-genotype (p.C282Y and p.H63D). The relationship between the natural logarithm of SF and time since menopause was examined using linear mixed models incorporating spline smoothing. For p.C282Y homozygotes, SF increased by a factor of 3.6 (95% CI (1.8, 7.0), P<0.001) during the first 10years postmenopause, after which SF continued to increase but at less than half the previous rate. In contrast, SF profiles for other HFE genotype groups increase more gradually and did not show a distinction between premenopausal and postmenopausal SF levels. Only p.C282Y homozygotes had predicted SF exceeding 200μg/L postmenopause, but the projected SF did not increase the risk of iron overload-related disease. These data provide the first documented evidence that physiological blood loss is a major factor in determining the marked gender difference in expression of p.C282Y homozygosity.

Fibroblast Fatty-Acid Oxidation Flux Assays Stratify Risk in Newborns with Presumptive-Positive Results on Screening for Very-Long Chain Acyl-CoA Dehydrogenase Deficiency

Very-long chain acyl-CoA dehydrogenase deficiency (VLCADD) is a clinically heterogeneous disorder with three major phenotypes: severe neonatal/infantile, milder childhood and late onset myopathic. VLCADD is genetically heterogeneous with numerous pathogenic mutations and variants of uncertain significance. VLCADD is included in many newborn screening programs but these suffer from high false positive rates, primarily due to positive screens in heterozygotes. Separating these and newborns with two low-risk “mild” variants from clinically at risk patients can be problematic, as clinical and biochemical markers are often unreliable, particularly in stable neonates. We have measured fibroblast fatty acid oxidation flux using [9,10-H3]myristic acid and [9,10-H3]oleic acid from 69 clinically presenting VLCADD patients including myopathic and infantile phenotypes and 13 positive newborn screened patients. We also measured fibroblast VLCADD enzyme activity by UV-HPLC detection of product in a sub-set of patients and compared these results to oleate FAO-flux. Fibroblast enzyme assay by UV-HPLC detection failed to clearly discriminate between some clinically presenting VLCADD patient cell lines and cell lines from some simple heterozygotes. FAO-flux clearly discriminated between clinically presenting VLCADD patients and the false positive screened patients. FAO-flux at 37 °C provides information as to the likely clinical phenotype but FAO-flux at 41 °C is the best discriminator for identifying clinically at risk patients.

Prevalence and audiological profiles of GJB2 mutations in a large collective of hearing impaired patients

Prevalence and audiological profiles of GJB2 mutations in a large collective of hearing impaired patients

Familial Mediterranean Fever: Clinical and Genetic Characteristics among Lebanese Pediatric Population

Objective: The aim of our study was to evaluate the clinical features, to define the frequency of mutation type, to assess genotype-phenotype correlation and the response to colchicine in childhood-onset Familial Mediterranean fever (FMF) in Lebanon. Methods: The characteristics of 550 children, presenting with FMF symptoms between January 2003 and January 2013 and having a positive Mediterranean fever gene (MEFV gene) mutation, were prospectively investigated. The clinical and genetic characteristics as well as the response to colchicine and its side effects were studied in 321 FMF children. The mutations were correlated with clinical presentation and disease severity. Results: Out of the 321 patients (183 males and 138 females), abdominal pain was the most common presenting feature documented in 84.7%. Mutational analysis detected simple heterozygotes, compound heterozygotes and homozygotes in 56.4%, 30.9% and 11.2% patients respectively. The most frequent mutation was M694V (37.2%), followed by E148Q mutation (27.4%). 71% patients received colchicine therapy; only 33.3% of them showed complete response. Genotype-phenotype correlation showed that M694V followed by E148Q was associated with moderate to severe disease form (71.6% and 62.7% respectively, P = 0.005). There was no association between mutation type and colchicine response. Conclusion: The most important features were the predominance of the M694V and E148Q. The M694V subgroup, followed by E148Q subgroup had a high disease severity score. Our data indicate an enhanced expression of the disease with E148Q mutation.

Spectrum of mutations of the LPL gene identified in Italy in patients with severe hypertriglyceridemia

BackgroundMonogenic hypertriglyceridemia (HTG) may result from mutations in some genes which impair the intravascular lipolysis of triglyceride (TG)-rich lipoproteins mediated by the enzyme Lipoprotein lipase (LPL). Mutations in the LPL gene are the most frequent cause of monogenic HTG (familial chylomicronemia) with recessive transmission. MethodsThe LPL gene was resequenced in 149 patients with severe HTG (TG > 10 mmol/L) and 106 patients with moderate HTG (TG > 4.5 and <10 mmol/L) referred to tertiary Lipid Clinics in Italy. ResultsIn the group of severe HTG, 26 patients (17.4%) were homozygotes, 9 patients (6%) were compound heterozygotes and 15 patients (10%) were simple heterozygotes for rare LPL gene variants. Single or multiple episodes of pancreatitis were recorded in 24 (48%) of these patients. There was no difference in plasma TG concentration between patients with or without a positive history of pancreatitis. Among moderate HTG patients, six patients (5.6%) were heterozygotes for rare LPL variants; two of them had suffered from pancreatitis. Overall 36 rare LPL variants were found, 15 of which not reported previously. Systematic analysis of close relatives of mutation carriers led to the identification of 44 simple heterozygotes (plasma TG 3.2 ± 4.1 mmol/L), none of whom had a positive history of pancreatitis. ConclusionsThe prevalence of rare LPL variants in patients with severe or moderate HTG, referred to tertiary lipid clinics, was 50/149 (33.5%) and 6/106 (5.6%), respectively. Systematic analysis of relatives of mutation carriers is an efficient way to identify heterozygotes who may develop severe HTG.