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Results for “compound heterozygosity”

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At least 19 recordsLinked to original sources

PubMed1989

Erythrocyte pyruvate kinase deficiency: a kinetic method for differentiation between heterozygosity and compound-heterozygosity.

The goal of the present study was to search for criteria that allow one to distinguish between normal individuals and heterozygotes as well as compound heterozygotes for pyruvate kinase (PK) deficiency. As the residual activity of PK with heterozygotes was between 35% and 110% of the normal activity, it was necessary to find other methods to prove heterozygosity. The PK in the hemolysates of 23 patients suffering from PK deficiency, 36 paternal and maternal enzymes as well as the enzymes of five heterozygous and four normal siblings together with those of 20 normal individuals, were studied according to the recommendations of the International Committee for Standardization in Haematology. The following hematological and enzyme kinetic parameters can serve to identify heterozygotes for PK deficiency: 1) a slight reticulocytosis, 2) an up-to-twofold increase of the intracellular concentrations of glucose-6-phosphate in the erythrocyte, 3) a mixed cooperativity of the phosphoenolpyruvate (PEP)-binding process of PK, 4) a decreased nucleotide specificity with guanosine diphosphate and uridine diphosphate, and 5) a lowered affinity for adenosine diphosphate. The most significant criterium found with all heterozygotes was a mixed cooperativity of the PEP-binding process caused by the presence of a mixture of normal and mutant PK.

Adolescent↗

PubMed2001

Compound heterozygosity for haemochromatosis gene mutations and hepatic iron overload in allogeneic bone marrow transplant recipients.

Iron overload has been proposed as a cause of liver dysfunction after BMT Factors which could be relevant to iron overload include the number of red cell transfusions and mutations within the haemochromatosis gene (HFE). Two point mutations, Cys282Tyr and His63Asp, have been described within HFE. Cys282Tyr homozygosity is associated with haemochromatosis; the effect of compound heterozygosity, Cys282Tyr/His63Asp, on iron status is variable. We analysed HFE status in 52 allograft patients surviving more than 6 months. Compound heterozygosity was identified in three patients (Cases 1-3). Iron status and liver function were evaluated and, in Cases 1 and 2, liver histology and iron content as well. Case 3 who received 12 units of red cells had a normal ferritin and liver function. Cases 1 and 2 received 29 and 59 units, respectively, and had high serum ferritins and transferrin saturations, abnormal liver function and significant hepatic iron overload on biopsy. Iron overload in Case 1 patient progressed in the context of GVHD and in the absence of further transfusion, suggesting that liver GVHD may increase hepatic iron accumulation. These cases demonstrate the variable phenotypic expression of HFE compound heterozygosity in BMT recipients, which may be only partly explained by transfusional iron loading. Venesection or chelation therapy should be considered in patients with coexistent hepatic GVHD and iron overload.

Adult↗

PubMed2002

Lethal neonatal and severe late infantile forms of carnitine palmitoyltransferase II deficiency associated with compound heterozygosity for different protein truncation mutations.

We describe a lethal neonatal form of carnitine palmitoyltransferase II (CPT II) deficiency with compound heterozygosity for 2 truncation mutations (Q413fs and 109AGC --> GCAGC). A new phenotype for a severe late infantile form of CPT II deficiency with hypoglycemia is associated with compound heterozygosity for the severe Q413fs mutation and a mild point mutation (P50H).

Carnitine O-Palmitoyltransferase↗

PubMed2002

Non-classical 21-hydroxylase deficiency in children: association of adrenocorticotropic hormone-stimulated 17-hydroxyprogesterone with the risk of compound heterozygosity with severe mutations.

AIM: To investigate the association between levels of 17-hydroxyprogesterone (17-OHP) and the risk of being compound heterozygous for severe mutations in children with non-classical 21-hydroxylase deficiency (NC21OHD). METHODS: In 86 Spanish NC21OHD children (75 families) an analysis of the 21-hydroxylase (21-OH) gene was performed by CYP21B-specific polymerase chain reaction amplification, allele-specific oligonucleotide hybridization and Southern blotting. Familial analysis established how the alleles segregated, and allowed the selection of 21-OH-genotyped normal and carrier children, which proved useful in determining a more precise definition of the cut-off for diagnosis. Receiver operating characteristics (ROC) curve analyses were performed to determine the potential value of 17-OHP in predicting compound heterozygosity for severe mutations. RESULTS: Thirty-four of the 86 children (39%) were found to carry one severe 21-OH mutation (7.3% deletions or conversions, 2.7% 655G, 2.7% Q318X, 1.3% 1172N, 1.3% R356W, and 3.3% double microconversions or small conversions involving single exons). The predominant mutation was V281L (56.7%). P453S and P30L were less frequent (3.3 and 2%). No patient showed two severe mutations. The degree of enzymic deficiency, as measured by basal or adrenocorticotropic hormone (ACTH)-stimulated 17-OHP levels in fully genotyped patients, but not clinical severity (age and number of symptoms at diagnosis), was found to be significantly greater in children with the severe/mild genotype. ROC curve analyses revealed a strong association between ACTH-17-OHP and genotype (area under the curve 0.908, SE 0.057). CONCLUSION: ACTH-stimulated 17-OHP may predict the risk of severe mutations in compound heterozygosity in children (maximum predictive value 93% sensitivity and 83% specificity for a cut-off at 151 nmol l(-1)), although a certain overlap in individual values is observed and performance of molecular analysis should never be obviated in the genetic counselling of these patients.

17-alpha-Hydroxyprogesterone↗

PubMed1999

Recessive Romano-Ward syndrome associated with compound heterozygosity for two mutations in the KVLQT1 gene.

We describe a Swedish family with the proband and his brother suffering from severe Romano-Ward syndome (RWS) associated with compound heterozygosity for two mutations in the KVLQT1 (also known as KCNQ1 and KCNA9) gene (R518X and A525T). The mutations were found to segregate as heterozygotes in the maternal and the paternal lineage, respectively. None of the heterozygotes exhibited clinical long QT syndrome (LQTS). No hearing defects were found in the proband. The data strongly indicates that the compound heterozygosity for R518X and A525T is the cause of an autosomal recessive form of RWS in this family. Our findings support the implication of a higher frequency of gene carriers than previously expected. We suggest that relatives of 'sporadic RWS' patients should be considered potential carriers, at risk of dying suddenly from drug-induced LQTS.

Child, Preschool↗

PubMed2000

beta-thalassemia intermedia caused by compound heterozygosity for Hb Malay (beta codon 19 AAC-->AGC; asn-->Ser) and codons 41/42 (-CTTT) beta(0)-thalassemia mutation.

We report a case of beta-thalassemia intermedia caused by compound heterozygosity for hemoglobin (Hb) Malay and codon 41/42 (-CTTT) beta(0)-thalassemia mutation in a 38-year-old Chinese woman. This patient has long-standing anemia with a baseline Hb level of around 70 g/L. She worked as a full-time cashier and had not required regular blood transfusions. Nevertheless, she had splenomegaly necessitating splenectomy, cholelithiasis, and iron overload. This case illustrates the varied phenotypic expression associated with compound heterozygosity for Hb Malay and other beta-thalassemia mutations. Since Hb Malay migrates as Hb A on electrophoresis and chromatography, this variant Hb mutation ought to be included in the differential diagnosis for beta-thalassemia major or intermedia patients of Southeast Asian descent who are reported to have Hb A on the basis of Hb analysis. The possible presence of this mutation should also be considered in appropriate cases for genetic counseling in couples at risk of conceiving fetuses with beta-thalassemia major or intermedia.

Adult↗

PubMed2007

Autosomal recessive von Willebrand disease associated with compound heterozygosity for a novel nonsense mutation (2908 del C) and the missense mutation C2362F: definite evidence for the non-penetrance of the C2362F mutation.

A novel null mutation (2908del C in exon 22) of the von Willebrand factor (VWF) gene was identified in compound heterozygosity with the missense mutation G7335T (C2362F) in exon 42 in a propositus from a new family with autosomal recessive von Willebrand disease (VWD). The propositus, referred at age 2 for severe epistaxis and prolonged bleeding after a tongue bite, had factor VIII:C 14-21 IU/dL, VWF Antigen 3-8 IU/dL and Ristocetin Cofactor activity < 3 IU/dL. Multimeric pattern showed the lack of triplet pattern and a faster mobility of central band, while heterozygotes for C2362F showed intermediate mobility compared to normal plasma and plasma from the propositus. In the propositus' family 5 subjects were heterozygotes for the C2362F mutation and 5 were heterozygotes for the cytosine deletion. Bleeding score was assessed with a detailed questionnaire in 28 heterozygotes for C2362F, 23 of whom identified in 5 previously reported families and 5 in the present one, and found to be similar to what is observed in normal controls and heterozygotes for null allele. In conclusion, the mutation C2362F is frequently observed in compound heterozygosity with null alleles in patients with recessive VWD in the Veneto region and cause bleeding only in the compound heterozygous or homozygous state.

Alleles↗

PubMed2001

Combined pituitary hormone deficiency caused by compound heterozygosity for two novel mutations in the POU domain of the Pit1/POU1F1 gene.

The POU homeodomain containing transcriptional activator POU1F1, formerly called Pit1 or GHF-1, is required for the embryological determination and postnatal secretory function of the GH-, PRL-, and TSH-producing cells in the anterior pituitary. Several mutations in the gene encoding POU1F1 have been described, resulting in a syndrome of combined pituitary hormone deficiency involving these three hormones. Most of the patients with this phenotype have either a dominant negative mutation in codon 271 (R271W) or are homozygous for a recessive mutation in the POU1F1 gene; to date only one case has been reported with compound heterozygosity for two point mutations. Here, we describe a boy with severe deficiencies of GH, PRL, and TSH who had compound heterozygosity for two novel point mutations in the POU1F1 gene: a 1-bp deletion frameshift mutation (747delA), the first one described to date in this gene, which leads to a nonfunctional truncated protein lacking the entire DNA recognition helix of the POU homeodomain, and a missense mutation in the C-terminal end of the fourth alpha-helix of the POU-specific domain (W193R),which causes a 500-fold reduction in the ability to bind to DNA and activate transcription.

Cell Line↗

PubMed2003

Compound heterozygosity for mutations (W156X and R225W) in SCN5A associated with severe cardiac conduction disturbances and degenerative changes in the conduction system.

Cardiac conduction defects associate with mutations in SCN5A, the gene encoding the cardiac Na+ channel. In the present study, we characterized a family in which the proband was born in severe distress with irregular wide complex tachycardia. His older sister died at 1 year of age from severe conduction disease with similarly widened QRS-complexes. Mutational analysis of SCN5A in the proband demonstrated compound heterozygosity for a nonsense mutation (W156X), inherited from the father, and a missense mutation (R225W), inherited from the mother. Genotyping on DNA extracted from tissue from the deceased sibling revealed the same SCN5A genotype. Injection of cRNA encoding the W156X mutation in Xenopus oocytes did not produce any current. The R225W substitution neutralizes the third Arg residue within the voltage-sensing segment of domain I. Expression studies showed that this mutation leads to a severe reduction in I(Na) and is also associated with gating changes. Histological examination of the heart from the deceased sibling revealed changes consistent with a dilated type of cardiomyopathy and severe degenerative abnormalities of the specialized conduction system. The occurrence of compound heterozygosity for these two mutations implies that the proband carries solely severely dysfunctional cardiac Na+ channels. This explains his severe phenotype and that of his deceased sister who had been a carrier of the same genotype. The morphological changes within the heart of the deceased sibling may have occurred secondary to the Na+ channel abnormality and contributed to the severity of the disorder in this individual.

Amino Acid Substitution↗

PubMed2003

Compound heterozygosity at the sphingomyelin phosphodiesterase-1 (SMPD1) gene is associated with low HDL cholesterol.

Type A and B forms of Niemann-Pick disease (NPD) are lipid storage disorders caused by deficient activity of the enzyme acid sphingomyelinase (aSMase) and the resulting accumulation of sphingomyelin in tissues. In the present study, we investigated two family members who had been diagnosed with Type B NPD and who had a severe decrease in plasma high density lipoprotein cholesterol (HDL-C). The proband (a 48-year-old male) had an HDL-C of 0.30 mmol/l (12 mg/dl) and his sister had values of 0.45 mmol/l (17 mg/dl) with severe premature coronary artery disease (CAD). Hypertriglyceridemia was found in both cases. aSMase activity measured in skin fibroblasts appeared markedly depressed. The SMPD1 gene, coding for aSMase, was sequenced in affected subjects and all family members. Compound heterozygosity (DeltaR608 and R441X) was identified in both affected patients. Carriers of the DeltaR608 mutation tended to have moderately to severe decreased HDL-C levels, whereas carriers of the R441X mutation, although present only in young subjects (<20 years of age) had normal HDL-C levels. To investigate the cause of the low HDL-C level in these patients, we studied apoA-I-mediated cellular cholesterol efflux in fibroblasts. Unlike patients with Tangier disease, cholesterol efflux was found to be normal under the experimental conditions used in the present study. On the other hand, we observed a significant increase in the free cholesterol:esterified cholesterol ratio in HDL fraction from these patients and a decrease in endogenous lecithin-cholesterol acyltransferase (LCAT) activity, as determined by the fractional esterification rate. Taken together, these results suggest that (1) compound heterozygosity at the SMPD1 gene causes a severe decrease in aSMase activity and in HDL-C and increases the risk of CAD, (2) this lipoprotein abnormality is not attributable to defective cellular cholesterol efflux, (3) abnormal HDL composition might cause a decrease in LCAT activity and a lack of HDL maturation.

Cholesterol, HDL↗

PubMed1996

Recurrent thrombosis due to compound heterozygosity for factor V Leiden and factor V deficiency.

A point mutation in the factor V gene (factor V Leiden) is the most common cause of familial thrombophilia. Patients with factor V Leiden have an increased risk of thrombosis, particularly those homozygous for the mutation. However, the phenotype in individuals with the mutation is variable, suggesting that other factors influence thrombotic risk. We describe for the first time a family in which two independent defects in factor V co-exist: heterozygosity for factor V Leiden and factor V deficiency. Compound heterozygosity for these two defects results in a phenotype similar to a homozygous factor V Leiden state with profound resistance to APC and recurrent thrombosis.

Adult↗

PubMed2005

A Japanese patient with familial Mediterranean fever associated with compound heterozygosity for pyrin variant E148Q/M694I.

Familial Mediterranean fever (FMF) is an inherited inflammatory disease occurring mainly in Mediterranean and Middle Eastern populations. FMF is caused by mutations in the MEFV gene that encodes pyrin/marenostrin. Here, we report a Japanese female FMF patient with heterozygosity for the compound pyrin E148Q/M694I showing recurrent fever, serositis or delay in skin wound healing. Her father and elder sister were heterozygous for pyrin variant M694I alone and sometimes suffered from mild fever or delay in wound healing, but her mother was heterozygous for pyrin variant E148Q alone and had no symptoms. This suggested that the inheritance of FMF occurred not only in an autosomal recessive manner but also in an autosomal dominant manner in this Japanese family, and the severity of the disease differed among the family members in relation to the mutation. In the treatment of FMF, colchicine, reserpine or prazosin hydrochloride have been reported to prevent the attacks, but, in our patient such drugs were ineffective or caused side effects, and only the anti-allergic drug azelastine was of benefit in relieving the attacks.

Adult↗

PubMed2004

Two cases of compound heterozygosity for Hb Hekinan [alpha27(B8)Glu-->Asp (alpha1)] and alpha-thalassemia in Thailand.

Two unrelated cases of compound heterozygosity for Hb Hekinan [alpha27(B8)Glu-->Asp (alpha1) and alpha-thalassemia have been found in Thailand. Mutations were established at protein level by peptide mapping and at the DNA level by direct sequence analysis. Proband S.S. had genotype - -SEA/alpha2(A)alpha1Hekinan, betaA/betaE, while an unrelated proband, S.J., is the first case described with the genotype - -SEA/alpha2(A)alpha1Hekinan, betaA/betaA. Both alpha1Hekinan mutations were located in the alpha1 locus. Hb Hekinan could not be accurately estimated by HPLC, since it was poorly separated from Hb A. However IEF gave good separation of Hb Hekinan and Hb A, leading to estimates of Hb Hekinan (alpha Hekinan 2/beta A 2 and alpha Hekinan 2/beta E 2) level as 40-43% of total Hb.

Adult↗

PubMed1993

Compound heterozygosity for hemoglobin C and Korle-Bu: moderate microcytic hemolytic anemia and acceleration of crystal formation [corrected].

We report here that compound heterozygosity for hemoglobin Korle-Bu (HbKB) and HbC (beta 6 Glu-->Lys) is associated with moderate chronic hemolytic anemia with microcytosis. To understand the pathogenesis of this syndrome, we have studied the effect of Hb Korle-Bu (KB = beta 73 Asp-->Asn) on the crystallization of HbC. We have previously established that fetal Hb (HbF) inhibits the crystallization of HbC. In contrast, HbS accelerates crystallization affecting the pathogenesis of SC disease. We now report on in vitro crystallization of mixtures of HbKB, HbC, and various amounts of HbF and the native hemolysate of a child who is a compound heterozygote for HbKB and HbC. At 6 months of age, the propositus' hemolysate contained 55% HbKB, 39% HbC, and 6% HbF. Crystal formed within 2 minutes compared with 30 minutes for the mixture of 40% HbC:60% HbS and with 180 minutes for 40% HbC:60% HbA. The morphology of the crystals formed was cubic, in contrast with the tetragonal crystals observed in CC and SC disease. Early crystals did not exhibit "sharp edges" until 45 minutes. Purified HbKB formed aggregates but not crystals after 24 hours. Isopycnic gradients showed that the KB/C compound heterozygotes have red blood cell (RBC) densities intermediate between the AC and CC phenotype and similar to SC disease. The surface residue beta 73, known to participate in areas of interaction of the deoxy HbS polymer, can now be assigned to areas of contact in HbC containing crystals. The hemolysis observed in the HbKB/C compound heterozygote is likely to be secondary to the acceleration of Hb crystallization. The microcytosis and increased RBC density is clearly the consequence of the presence of HbC, but the basis of the increased RBC pathology compared with AC trait, despite the low proportion of HbC (35% to 40%), remains to be elucidated.

Adolescent↗

PubMedDate not supplied

Compound heterozygosity for hemoglobin Knossos [alpha 2 beta 2 27 (B9) Ala-Ser] and IVS I-1 mutation.

A three-year-old female with compound heterozygosity for Hb Knossos and IVS-I-1 mutation is presented. On physical examination she had no abnormality except for pallor. Hb was 6.9 g/dl, MCV 61 fl, Hb A2 2% and Hb F 38.5%. Acrylamidegel electrophoresis at a pH of 6 revealed the presence of Hb Knossos in the child and her father. DNA studies revealed that the child was compound heterozygous for Hb Knossos and the IVS I-1 mutation. When the clinical expression of this combination in a previously reported patient with Hb Knossos/FSC8 mutation is compared, it is shown that the newly presented patient has a more severe condition, indicating that the mutations in the trans of Hb Knossos may play a role in the phenotypical expression of the disease.

Anemia↗

PubMed1994

Molecular genetic characterization and urinary excretion pattern of metabolites in two families with MCAD deficiency due to compound heterozygosity with a 13 base pair insertion in one allele.

Two families with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency due to compound heterozygosity are described. All patients have a 13 bp insertion in exon 11 of one allele at the MCAD gene locus. In the other allele patients in one of the families harbour the prevalent G985 mutation, and the other family possess an unidentified mutation causing reduced levels of MCAD mRNA. We demonstrate that the disease in these families is inherited as an autosomal recessive trait. Individuals heterozygous for the mutations show heterozygous/control levels of beta-oxidation activities in cultured fibroblasts (9.1-16.3 pmol/min per mg protein; control 10-17 pmol/min per mg protein), and in the excretion of the 'beta-oxidation metabolites', hexanoylglycine (< 2 mumol/mmol creatinine), suberylglycine (< 2 mumol/mmol creatinine) and phenylpropionylglycine (< 2 mumol/mmol creatinine). This shows that there is no 'negative dominance' from the mutant monomeric protein onto the normal ones, in accordance with the finding of low levels of MCAD mRNA from the allele harbouring the 13 bp insertion as well as the allele with the unidentified mutation, and the low steady-state level of enzyme protein expressed from the G985-bearing allele. In the family possessing the G985 and the 13 bp insertion mutations, two asymptomatic compound heterozygous individuals were detected. They exhibited elevated excretion of hexanoylglycine (5-15 mumol/mmol creatinine) and suberylglycine (4-13 mumol/mmol creatinine), together with beta-oxidation activity in fibroblasts in the homozygous range (2.9 pmol/min per mg protein), showing a lack of correlation between the genotype, some biochemical parameters and the clinical phenotype.

Acyl-CoA Dehydrogenase↗

PubMed1990

Compound heterozygosity for a mild beta (+) and a rare beta(0)-thalassemia allele.

Hematological and hemoglobin composition data are presented for 14 members of a Surinam family (and for 1 unrelated subject) with either a beta-thalassemia heterozygosity [5 with the -29 (A----G) beta + mutation and 5 with the IVS II-849 (A----G) beta(0) mutation] or a compound heterozygosity (the 5 remaining patients). Identification of the mutation was by hybridization of amplified DNA with 32P-labelled synthetic oligonucleotides. The data indicate distinct differences between the two groups of heterozygotes, mainly in degree of microcytosis and hypochromia, in Hb A2 level, and in the level of G gamma (high in the -29 heterozygotes and low in the IVS II-849 heterozygotes). The 5 compound heterozygotes had a thalassemia intermedia with high Hb F levels (high G gamma), elevated Hb A2, and Hb A levels comparable to those seen in patients with a homozygosity for the -29 mutation or with the combination of this beta(+)-thalassemia and Hb S. An alpha-thalassemia-2 heterozygosity (-3.7 kb deletion) was present in 2 patients. Their hematological data were improved over those for the patients with four alpha globin genes; one was the mother of two sets of twins. The high G gamma value in the Hb F of the compound heterozygotes suggests that the high Hb F production in the condition is mainly directed by the chromosome with the -29 (A----G) mutation.

Adult↗

PubMed1998

Molecular bases of pseudo-homozygous APC resistance: the compound heterozygosity for FV R506Q and a FV null mutation results in the exclusive presence of FV Leiden molecules in plasma.

Pseudo-homozygous APC resistance, the condition resulting from compound heterozygosity for FV R506Q (FV Leiden) and quantitative FV deficiency, provides a natural model to study the interaction between procoagulant and anticoagulant defects. This paper reports a complete FV characterization of a pseudo-homozygous APC resistant thrombotic patient. The expression of the patient's non-Leiden gene was found to be severely impaired both at the mRNA and protein levels. In particular, only FV Leiden molecules were detected in the patient's plasma by immunoblotting, which accounts for the observed marked APC resistance. Analysis of the FV cDNA obtained by reverse transcription of platelet RNA revealed that the mRNA of the non-Leiden gene was extremely reduced in amount. A PAC clone containing the whole FV gene was used to design primers for a complete FV exon scanning. A 2-bp insertion at nucleotide 3706 in the large exon 13 of the non-Leiden gene, predicting a frame-shift and premature termination of protein synthesis, was identified as responsible for the FV defect. Failure to find any case of pseudo-homozygous APC resistance in a large sample (6,804) of blood donors suggests that this condition is extremely rare among normal controls and that its detection is favoured by the thrombotic risk that it may confer.

Aged↗