H. G. Koch

Prothrombin G20210A Gene Mutation and Further Prothrombotic Risk Factors in Childhood Thrombophilia

Risk factors for venous thrombosis in adults are the prothrombin G20210A and the factor V (FV) G1691A mutations and hereditary deficiencies of protein C, protein S and antithrombin. However, data are limited on the relevance of these risk factors for thrombosis in children and adolescents. We therefore investigated 261 patients aged 0 to 18 (median 5.7 years, 48% male) with venous thrombosis and controls (n=370) for the presence of prothrombotic risk factors including the prothrombin G20210A mutation. The following frequencies of hereditary risk factors (patients versus controls), odds ratios (OR) and 95% confidence intervals (CI), or results of Fishers exact test, respectively, were found: prothrombin G20210A, 4.2% versus 1.1%, OR/CI 4.1/1.3 to 12.8; FV G1691A, 31.8% versus 4. 1%, OR/CI 11.0/6.2 to 19.7; protein C deficiency, 9.2% versus 0.8%, OR/CI 12.4/3.7 to 41.6, protein S deficiency, 5.7% versus 0.8%, OR/CI 7.5/2.1 to 26.0; antithrombin deficiency in 3.4% in the patients, but not in the controls, P=0.0003. The prothrombin mutation was combined with the heterozygous FV G1691A mutation (2. 3%) or protein C deficiency (0.3%) in the patients, but not in the controls (prothrombin and FV mutation, P=0.0048; prothrombin and protein C deficiency, not significant). The carrier frequencies and ORs of all hereditary risk factors showed a non-significant trend toward higher prevalences in patients suffering spontaneous thrombosis, compared with those with an additional underlying disease. In conclusion, the prothrombin G20210A and the FV G1691A mutation, deficiencies of protein C, protein S, and antithrombin are important risk factors for venous thrombosis during childhood and adolescence.

Infant methylenetetrahydrofolate reductase 677TT genotype is a risk factor for congenital heart disease

OBJECTIVE Recently, an association between the homozygous C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene in infants with congenital neural tube defects or congenital oral clefts has been shown. However, no data are available so far with respect to the MTHFR 677TT genotype in children with underlying structural congenital heart disease (CHD). METHODS We investigated the MTHFR genotype in 114 Caucasian CHD patients aged newborn to 16 years (median 0.6 years; 53% male) and in 228 age- and sex-matched healthy controls. RESULTS In childhood patients with CHD the homozygous MTHFR 677TT genotype was found in 21 out of 114 subjects (18.4%) compared with 21 out of 228 controls (9.2%; odds ratio (OR) 2.2, 95%-confidence interval (CI) 1.2-4.3; P=0.027). In patients with pulmonary valve stenosis, hypoplastic left heart syndrome, coarctation of the aorta, aortic valve stenosis or subaortic stenosis the frequency of the TT genotype varied between 38 and 67% with corresponding ORs from 6.1 (CI, 1.4-27.5; P=0.034) to 20.4 (CI, 1.8-235.0; P=0.025), whereas in other structural CHD the frequency of this genotype was not significantly different from the controls. CONCLUSIONS With the present study we can show for the first time that the embryonal MTHFR 677TT genotype is significantly associated with the development of structural congenital heart malformations during early pregnancy. It remains to be clarified, whether this genotype is at least a risk marker or a risk factor for structural congenital heart malformations.

Factor V Leiden, protein C, and lipoprotein (a) in catheter-related thrombosis in childhood: A prospective study

OBJECTIVE To determine the association between catheter-related thromboses and hereditary causes of thrombophilia, including the factor V Leiden mutation, deficiencies of protein C or protein S, or increased lipoprotein (a). STUDY DESIGN To evaluate the incidence of genetic risk factors for familial thrombophilia in catheter-related thrombosis, 163 consecutively admitted infants and children (cardiac disease and catheter placement [C] n = 140; Broviac catheter [B] n = 23) were prospectively investigated. In addition, an age-matched, healthy control group undergoing elective surgery (S: n = 155) was investigated. RESULTS Heterozygous factor V Leiden mutation was diagnosed in 20 of the 318 study subjects (C: n = 5; B: n = 4; S: n = 11), homozygous factor V Leiden mutation was found in two subjects (C: n = 1; S: n = 1), protein C deficiency type I was diagnosed in nine subjects (C: n = 4; B: n = 1; S: n = 4), and five subjects showed increased lipoprotein (a) (C: n = 3; S: n = 2). The frequency of thrombosis (C: n = 13; B: n = 5) in patients with familial thrombophilia was significantly higher (p < 0.0001; chi square: 27.79) in the catheter groups (15 of 17 subjects) than in control subjects after minor elective surgery (none of 18). Fifteen of the 18 infants with thrombosis had congenital thrombophilia; two children with congenital thrombophilia did not have documented thrombosis, and three infants with vascular occlusion had no inherited predisposition to thrombophilia. CONCLUSIONS Genetic risk factors for familial thrombophilia play an important role in the manifestation of catheter-related thromboembolism in children.

Multicentre evaluation of combined prothrombotic defects associated with thrombophilia in childhood

Abstract To evaluate the role of multiple established and potential causes of childhood thrombophilia, 285 children with a history of thrombosis aged neonate to 18 years (first thrombotic onset) were investigated and compared with 185 healthy peers. APC- resistance (FV:Q506), protein C, protein S, antithrombin, heparin cofactor II (HCII), histidine-rich glycoprotein (HRGP), and prothrombin (F.II), factor XII (F.XII), plasminogen, homocysteine and lipoprotein (a) (Lp(a)) were investigated. In 59% of patients investigated one thrombotic defect was diagnosed, 19.6% showed two thrombotic risk factors, while in 21.4% of children investigated no risk factor could be identified. Single defects comprised established causes of inherited thrombophilia: FV:Q506 (homozygous n = 10, heterozygous n = 69), protein C (homozygous n = 1; heterozygous n = 31), heterozygous type I deficiency states of protein S (n = 7), antithrombin (n = 7) and homocystinuria (n = 6); potentially inherited clotting abnormalities which may be associated with thrombophilia: F.XII (n = 3), plasminogen (n = 2), HCII (n = 1), increased HRGP (n = 4); new candidate risk factors for thrombophilia: elevated plasma levels of Lp(a) (n = 26), F.II (n = 1). Heterozygous FV:Q506 was found in combination with heterozygous type I deficiency states of protein C (n = 2), protein S (n = 13), antithrombin (n = 8) and HCII (n = 1), increased Lp(a) (n = 13), and once each with elevated levels of F.II, moderate hyperhomocysteinemia, fibrinogen concentrations >700 mg/dl and increased HRGP. In addition to the association with FV:Q506, heterozygous protein C type I deficiency was combined with deficiencies of protein S (n = 2), antithrombin (n = 1), and increased Lp(a) (n = 3). One patient showed protein C deficiency along with familially increased von Willebrand factor >250%. Besides coexistence with FV:Q506 and protein C deficiency, protein S deficiency was combined with decreased F.XII and increased Lp(a) in one subject each. Furthermore, we found combinations of antithrombin deficiency/elevated Lp(a), hyperhomocysteinemia/Lp(a), deficiency of HCII/plasminogen, and plasminogen deficiency along with increased Lp(a) each in one. Increased prothrombin levels were associated with fibrinogen concentrations >700 mg/dl and with HCII deficiency in one child each. Carrier frequencies of single and combined defects were significantly higher in patients compared with the controls. Conclusion In conclusion, data of this multicentre evaluation indicate that paediatric thromboembolism should be viewed as a multifactorial disorder.

Deficits in selective and sustained attention processes in early treated children with phenylketonuria — result of impaired frontal lobe functions?

Twenty normally intelligent children with early treated phenylketonuria (PKU) (IQ: mean=101.4, SD=10.0; age: mean=10 years 11 months, SD=1.3 years) and 20 healthy controls, matched for age, sex and IQ, were assessed for their selective (Stroop Task) and sustained attention (Test-d-2). Using positron emission tomography an activation of the frontal lobe during the Stroop task had previously been demonstrated. In addition to the Stroop Task and the Test-d-2, a short-term memory test as a “non-frontal-lobe-function-task” was administered to all subjects. Group comparisons demonstrated that PKU children had specific deficits in selective and sustained attention, which were significantly correlated with the concurrent serum phenylalanine concentration.ConclusionThe results give evidence that even dietary treated children with PKU were suffering from impaired attentional control mechanisms in spite of a normal IQ. The deficits might be the result of impaired frontal lobe functions.

Normal Clinical Outcome in Untreated Subjects with Mild Hyperphenylalaninemia

There is international consensus that patients with phenylalanine (Phe) levels <360 μM on a free diet do not need Phe-lowering dietary treatment whereas patients with levels >600 μM do. Clinical outcome of patients showing Phe levels between 360 and 600 μM in serum on a free nutrition has so far only been assessed in a small number of cases. Therefore, different recommendations exist for patients with mild hyperphenylalaninemia. We investigated in a nationwide study 31 adolescent and adult patients who persistently displayed serum Phe levels between 360 and 600 μM on a normal nutrition with a corresponding genotype. Because of limited accuracy of measurements, Phe levels should be looked on as an approximation, but not as an absolute limit in every instance. In addition to serum Phe levels, the assessment program consisted of comprehensive psychological testing, magnetic resonance imaging of the head, 1H magnetic resonance spectroscopy, and genotyping. We found a normal intellectual (intelligence quotient, 103 ± 15; range, 79–138) and educational (school performance and job career) outcome in these subjects as compared with healthy control subjects (intelligence quotient, 104 ± 11; range, 80–135). Magnetic resonance imaging revealed no changes of cerebral white matter in any patient, and 1H magnetic resonance spectroscopy revealed brain Phe levels below the limit of detection (<200 μM). In the absence of any demonstrable effect, dietary treatment is unlikely to be of value in patients with mild hyperphenylalaninemia and serum Phe levels <600 μM on a free nutrition, and should no longer be recommended. Because of a possible late-onset phenylketonuria, Phe levels of untreated patients should be monitored carefully at least during the first year of life. Nevertheless, problems of maternal phenylketonuria should still be taken into account.

Factor V Leiden and genetic defects of thrombophilia in childhood porencephaly

AIMS To determine to what extent the Arg506 to Gln point mutation in the factor V gene and further genetic factors of thrombophilia affect the risk of porencephaly in neonates and infants. METHODS The Arg506 to Gln mutation, factor V, protein C, protein S, antithrombin, antiphospholipid antibodies and lipoprotein (a) (Lp(a)) were retrospectively measured in neonates and children with porencephaly (n=24). RESULTS Genetic risk factors for thrombophilia were diagnosed in 16 of these 24 patients: heterozygous factor V Leiden (n=3); protein C deficiency type I (n=6); increased Lp (a) (n=3); and protein S type I deficiency (n=1). Three of the 16 infants had two genetic risk factors of thrombophilia: factor V Leiden mutation combined with increased familial Lp (a) was found in two, and factor V Leiden mutation with protein S deficiency type I in one. CONCLUSIONS The findings indicate that deficiencies in the protein C anticoagulant pathway have an important role in the aetiology of congenital porencephaly.

Neurological findings in early treated phenylketonuria

Twenty early treated, normal intelligent patients (IQ: mean 101.4, SD 10.0; age: mean 10.11, SD 1.3 years) with classical phenylketonuria and 20 age–, sex– and IQ–matched healthy controls were investigated for neurological outcome, especially with regard to fine motor ability using the motor performance task (“Motorische Leistungsserie”). No pathological findings were seen on clinical neurological examination. The patient group had significantly poorer results in a concentration task (Test–d–2) as well as in some subtests of the motor performance task. Patients had difficulties in tasks which needed speed and precision of arm–hand–finger movements. High serum phenylalanine concentrations were significantly correlated with these deficiencies in fine motor ability. Our data demonstrated mild neurological impairment even in early and relatively strictly treated patients with phenylketonuria.

Prothrombotic risk factors in children with spontaneous venous thrombosis and their asymptomatic parents: a family study.

The present study was designed to assess to what extent single and combined clotting abnormalities influence spontaneous vascular accidents in pediatric patients, and how the children affected differ in their prothrombotic risk profiles from their biological first-degree family members. In addition, this study was performed to investigate if relatively mild thrombophilic polymorphisms not leading to thrombosis in the parents cause severe clinical expression when coinherited with an established prothrombotic risk factor. The factor V (FV) G1691A mutation, the prothrombin (PT) G20210A variant, the methylenetetrahydrofolate reductase (MTHFR) T677T genotype, the plasminogen activator inhibitor (PAI)-1 promoter polymorphism, lipoprotein (Lp)(a), antithrombin, protein C, and protein S were investigated in 48 childhood patients aged neonate to <18 years (median 0.5 years) with spontaneous venous thromboembolism (SVT) compared with the carrier status of their first-degree family members. In 19 of the 48 patients (39.6%), one prothrombotic risk factor was diagnosed, and in 27 of the 48 subjects (56.3%) at least two prothrombotic defects/alleles. In the majority of cases with SVT, the FV G1691A mutation was involved either with a second mutated allele or combined with elevated Lp(a), the 4G/4G genotype of the PAI -1 promoter polymorphism, and the T677T MTHFR genotype. The rate of combined prothrombotic risk factors was significantly higher in childhood patients compared with their parents. In conclusion, based on the data presented here we suggest that early-onset SVT in childhood patients is mainly caused by combinations of at least two prothrombotic risk factors.

The 677T genotype of the common MTHFR thermolabile variant and fasting homocysteine in childhood venous thrombosis

Abstract Controlled data on the association of MTHFR genotypes, hyperhomocysteinaemia and their interaction with factor V G1691A with childhood thrombosis are not yet available. Therefore we conducted a case-control study comparing 141 childhood patients with venous thrombosis with 345 healthy controls. The MTHFR C677T genotypes, FV G1691A and prothrombin G20210A were evaluated; in addition, fasting homocysteine concentrations were measured in a subgroup of 60 children and 80 healthy controls. 10.4% of the healthy control population showed the MTHFR TT genotype, 34.2% the CT genotype and 55.4% the CC variant. MTHFR genotypes account for fasting homocysteine concentrations in healthy controls (CC: 5.5 μmol/l (4–7.2); CT: 7 μmol/l (3.9–9.8); TT: 12.1 μmol/l (7.7–13.3)) with an upper age-specific 95th percentile of 8.3 μmol/l. The following frequencies (patients versus controls), odds ratios (OR) and 95% confidence intervals (CI) were found for single defects: MTHFR 677TT genotype (10.6% vs. 10.4%; OR/CI: 1.02/0.54–1.93; P= 0.99) and CT genotype (43.8% vs. 34.2%; OR/CI: 2.12/1.42–3.16; P= 0.0000). A combination of FV G1691A mutation and MTHFR 677CT genotype was found in 9.9% of patients and in 2.9% of the controls (OR/CI: 3.8/1.64–8.75; P= 0.027). Fasting homocysteine median (range) concentrations in the patient group were significantly higher than in the controls (7 μmol/l (3–23) vs. 5.5 μmol/l (3–8.4); P= 0.0004), and homocysteine concentrations >8.3 μmol/l were found in 40% of patients vs. 2.5% of the controls (OR/CI: 22/2.64–183; P= 0.0003). Conclusion Data of this childhood case-control study suggest that mildly elevated fasting homocysteine concentrations >8.3 μmol/l and the CT genotype of the MTHFR C677T variant are significant risk factors for venous vascular occlusion in children.