ABCMdb

PMID: 17015492

Scotet V, Audrezet MP, Roussey M, Rault G, Dirou-Prigent A, Journel H, Moisan-Petit V, Storni V, Ferec C
Immunoreactive trypsin/DNA newborn screening for cystic fibrosis: should the R117H variant be included in CFTR mutation panels?
Pediatrics. 2006 Nov;118(5):e1523-9. Epub 2006 Oct 2., [PubMed]

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No. Mutations Sentence Comment

5 ABCC7 p.Arg117His A monthly ARTICLE Immunoreactive Trypsin/DNA Newborn Screening for Cystic Fibrosis: Should the R117H Variant Be Included in CFTR Mutation Panels? Login to comment 10 ABCC7 p.Arg117His The panels of mutations used in most cystic fibrosis newborn screening programs enable the detection of a relatively frequent CFTR variant (R117H) whose implication in cystic fibrosis remains unclear. Login to comment 13 ABCC7 p.Arg117His The aim of this study was to describe the clinical outcome of the children found to be compound heterozygous for R117H by screening in Brittany (western France), where cystic fibrosis newborn screening was set up in 1989, and to assess whether this CFTR variant should be included in the newborn screening mutation panels. METHODS. Login to comment 16 ABCC7 p.Arg117His Since our screening protocol has enabled detection of R117H (ie, in 1995), 360 466 newborns have been screened for cystic fibrosis in Brittany, of whom 124 had elevated immunoreactive trypsin and 2 mutations in the CFTR gene. Login to comment 17 ABCC7 p.Arg117His Nine of these children (7.3%) were compound heterozygous for R117H, which in all cases was linked to the 7T࿝11TG haplotype [IVS8-nT variant/m(TG) repeat]. Login to comment 18 ABCC7 p.Gly551Asp ABCC7 p.Arg117His ABCC7 p.Arg117His ABCC7 p.Arg117His Their genotypes were F508del/R117H (n ϭ 7), I507del/R117H (n ϭ 1), or G551D/ R117H (n ϭ 1). Login to comment 19 ABCC7 p.Arg117His At the time of this writing, the mean age of these 9 children was 7.0 years (the oldest being Ͼ10 years of age), and none of them had yet developed www.pediatrics.org/cgi/doi/10.1542/ peds.2005-3161 doi:10.1542/peds.2005-3161 Key Words cystic fibrosis, newborn screening, R117H, genetic counseling, Brittany Abbreviations CF-cystic fibrosis CFNS-cystic fibrosis newborn screening IRT-immunoreactive trypsin CFTR-cystic fibrosis transmembrane conductance regulator nT-n thymidines FEV1-forced expiratory volume in 1 second FVC-forced vital capacity Accepted for publication May 24, 2006 Address correspondence to Claude Fe´rec, MD, PhD, Inserm U613 Ge´ne´tique Mole´culaire et Ge´ne´tique E´pide´miologique, Laboratoire de Ge´ne´tique Mole´culaire, EFS-Bretagne, 46 Rue Fe´lix Le Dantec, BP 62026, 29220 Brest Cedex 2, France. Login to comment 22 ABCC7 p.Arg117His Moreover, we observed that, in Brittany, all the patients carrying the R117H variant have been identified exclusively through cystic fibrosis newborn screening. Login to comment 24 ABCC7 p.Arg117His ABCC7 p.Arg117His In view of the high frequency of R117H-7T identified by cystic fibrosis newborn screening, the uncertain outcome of the asymptomatic children, and physicians` difficulty in managing these situations, we propose the withdrawal of the R117H variant from the panels of CFTR mutations used in cystic fibrosis newborn screening, given the expanding implementation of cystic fibrosis newborn screening. Login to comment 28 ABCC7 p.Arg117His In France, the molecular part of the screening protocol relies on the use of a kit of 30 mutations (Elucigene CF30; Tepnel Diagnostics Ltd, Abingdon, Oxfordshire, United Kingdom), and the first results of this program have revealed the high frequency of one variant (R117H), which now seems to be the most frequent after the main F508del mutation. Login to comment 29 ABCC7 p.Arg117His The first 2-year experience of the French CFNS program shows that this variant has been found in 7.2% of the newborns screened positive with 2 CFTR mutated alleles (18 of 249 newborns, including 16 compound heterozygotes for R117H and 2 homozygotes for this variant).4 Similar findings have been reported elsewhere. Login to comment 30 ABCC7 p.Arg117His For example, CFNS in Massachusetts found that 8.0% of the CF-affected newborns carried R117H as 1 of their 2 abnormal CFTR alleles (9 of 112).5 The situation is quite different, however, in the CFNS program of Wisconsin, where this frequency reaches 26.7% (8 of 30 newborns detected from March 2002 to June 2003).6 Because these 8 infants had normal or borderline sweat-test values, they were not included in the calculation of CF incidence in the state. Login to comment 31 ABCC7 p.Arg117His The R117H variant, which is located in exon 4 of the CFTR gene, belongs to the class IV mutations, which are known to produce a CFTR protein that affect ion conductance.7 The implication of this variant in CF remains ambiguous. Login to comment 32 ABCC7 p.Arg117His The phenotype of subjects who are compound heterozygous for a severe CFTR mutation and R117H can range from a classical form of CF to congenital bilateral absence of vas deferens or even to no clinical disease, especially in women. Login to comment 33 ABCC7 p.Arg117His This large phenotypic heterogeneity may be explained in part by the efficiency of exon-9 splicing, which is influenced by a polythymidine sequence of intron 8 of the CFTR gene (IVS8-nT), which can include a succession of 5 (5T), 7 (7T), or 9 thymidines (9T).8 The length of this tract influences the efficiency of mRNA splicing, with a decrease in mature functional CFTR protein observed for the shorter alleles.9-11 This is why a given F508del/R117H genotype can be associated with a mild form of CF characterized by pancreatic sufficiency and moderate lung disease (when it is found in cis with the 5T allele), with male infertility only, or even with absence of any clinical signs (when it is found in cis with the 7T allele).8,12-15 The efficiency of mRNA splicing is also modulated by the length of a polymorphic TG locus [m(TG)], which is located just upstream of the polythymidine sequence. Login to comment 34 ABCC7 p.Arg117His The number of TG repeats ranges from 9 to 13, and a decrease in mature functional CFTR protein is observed for the longer alleles.16 According to the North American Cystic Fibrosis Foundation Consensus Panel,17 only the R117H-5T haplotype is considered to be a disease-causing mutation, but this is still a matter of debate in the clinical community. Login to comment 35 ABCC7 p.Arg117His ABCC7 p.Arg117His ABCC7 p.Arg117His The other form (R117H-7T) is detected most frequently in the screening protocols (frequency ranges from 70% to 100% in white populations).6,18-20 Whereas R117H-5T acts as a deleterious mutation, the situation is less clear for R117H-7T. Login to comment 36 ABCC7 p.Arg117His Most subjects who are compound heterozygous for R117H on a 7T background have normal or borderline sweat test results, and it is probable that the majority of them will not progress toward CF symptomatology. Login to comment 38 ABCC7 p.Arg117His Because the outcome of children found to be compound heterozygous for R117H-7T remains difficult to predict at this time, it is hard to offer satisfactory genetic counseling to the families concerned.23 There are questions of how to counsel the parents: Which information should be given to the parents of a compound heterozygous child with normal sweat test results? Login to comment 43 ABCC7 p.Arg117His The aim of this article was to review the data of the 16 years of experience of CFNS in Brittany in order to present the clinical outcome of the children screened positive with an R117H-7T and a second severe CFTR mutation. Login to comment 44 ABCC7 p.Arg117His To date, our screening protocol has identified 9 children as compound heterozygous for R117H, which in all cases was linked to the IVS8-7T variant. Login to comment 45 ABCC7 p.Arg117His These data lead us to reconsider our position and to wonder whether R117H should be included in mutation panels. METHODS Newborn Screening for CF in Brittany A pilot program of newborn screening for CF was implemented in Brittany in 1989.1 Since then, 2 protocols have successively been used: first an IRT/IRT protocol and then, from 1992, an IRT/DNA analysis protocol. Login to comment 48 ABCC7 p.Arg117His This extended molecular analysis had enabled the detection of the R117H variant since 1995. Login to comment 49 ABCC7 p.Arg117His Since the implementation of the CFNS program in the whole of France in 2002, the initial analysis of 3 exons of the CFTR gene has been replaced by the use of a kit of 30 mutations (Elucigene CF30), which directly enables identification of the R117H variant. Login to comment 52 ABCC7 p.Arg117His Study Population Our study population was the cohort of children screened for CF in Brittany since 1995, when the CFNS protocol first enabled detection of the R117H variant. Login to comment 54 ABCC7 p.Arg117His Among them, 124 were screened positive (ie, with an elevated IRT level and 2 mutations in the CFTR gene), of whom 9 were found to be compound heterozygous for R117H. Login to comment 56 ABCC7 p.Arg117His Assessment of Clinical Status The clinical status at the last follow-up visit of the 9 children who are compound heterozygous for R117H and of the 9 control children was documented by the referring physicians. Login to comment 59 ABCC7 p.Arg117His Statistical Analysis We assessed the frequency of the R117H variant in the cohort of newborns who screened positive for CF in Brittany since 1995. Login to comment 61 ABCC7 p.Arg117His ABCC7 p.Arg117His Finally, we compared the frequency of R117H in the cohort of newborns screened positive for CF with that observed in a cohort of CF patients born in Brittany before the CFNS protocol enabled the detection of the R117H (1960-1994 period). Login to comment 64 ABCC7 p.Arg117His RESULTS Pilot newborn screening for CF was implemented in Brittany in 1989 and has enabled the detection of the R117H variant since 1995. Login to comment 66 ABCC7 p.Arg117His Nine of these children (7.3%) were compound heterozygous for R117H, which was only associated with the 7T࿝11TG haplotype. Login to comment 67 ABCC7 p.Gly551Asp ABCC7 p.Arg117His ABCC7 p.Arg117His ABCC7 p.Arg117His Their genotypes were F508del/R117H (n ϭ 7), I507del/R117H (n ϭ 1), or G551D/R117H (n ϭ 1). Login to comment 70 ABCC7 p.Arg117His At the time of this writing, the mean age of these children was 7.0 years (range: 4.0-10.9 years), and none of TABLE1ClinicalOutcomeofthe9ChildrenScreenedatBirthinBrittanyWhoAreCompoundHeterozygousforR117H-7T(1995-2004) CaseCase1Case2Case3Case4Case5Case6Case7Case8Case9 GenderFMMFMMMFF Yearofbirth199519951997199719992001200220022002 Currentage,y10.910.48.98.86.84.84.24.24.0 Ageatthelastvisit,y10.21.37.6-5.73.21.83.03.0 GenotypeG551D/R117HF508del/R117HF508del/R117HF508del/R117HI507del/R117HF508del/R117HF508del/R117HF508del/R117HF508del/R117H IVS8-nT/m(TG)7T_11TG7T_11TG7T_11TG7T_11TG7T_11TG7T_11TG7T_11TG7T_11TG7T_11TG IRT900␮g/L1840␮g/L1675␮g/L1700␮g/L1175␮g/L1190␮g/L90ng/mL157ng/mL60ng/mL Sweattest,mEq/L453156-4035291835 MeconiumileusNoNoNoNoNoNoNoNoNo PancreaticstatusPSPSPS-PSPSPSPSPS Anthropometry Height,cm(zscore)141.0(1.0)97.5(-0.3)125.0(0.4)-108.0(-0.9)102.0(1.9)-100.8(2.5)92.0(-0.2) Weight,kg(zscore)35.0(1.4)13.0(-2.1)22.2(-0.5)-16.7(-1.2)16.5(2.0)11.3(-0.6)17.0(2.5)13.8(0.1) BMI,kg/m217.613.714.2-14.315.9-16.716.3 Pulmonaryfunction FEV1,L(%)NotperformedNotperformed1.91(132.4)-(116.1)NotperformedNotperformedNotperformedNotperformed FVC,L(%)NotperformedNotperformed2.20(128.6)-(123.7)NotperformedNotperformedNotperformedNotperformed IntravenousantibioticcuresNoNoYes-NoNoNoNoNo Ifyes,n(during)2(10d)- HospitalizationsNoneNoneNone-NoneNoneNoneNoneNone ComplicationsNoneNoneNone-NoneNoneNoneNoneNone ConclusionVerygoodnutritional andpulmonary status Perfectclinical exam Verygood growth Lostatfollow-upGoodgrowth, good clinical evolution Satisfactory evolution Satisfactory evolution Verygoodnutritional status,verygood development Goodclinical state PSindicatespancreaticsufficiency;-,datanotavailable. Login to comment 78 ABCC7 p.Arg117His Despite the small sample size, this comparison highlighted the fact that the genotypes including R117H were associated with lower IRT levels (1413.3 [SD: 374.9] vs 2038.3 [SD: 443.4] ␮g/L; P ϭ .030), lower sweat chloride concentrations (36.1 [SD: 11.3] vs 96.2 [SD: 19.9] mEq/L; P Ͻ .001), less frequent hospitalizations (0 of 8 vs 6 of 9; P ϭ .009) and seemed to have better pulmonary function, evidenced by higher spirometric data (FEV1: P ϭ .051; FVC: P ϭ .053). Login to comment 79 ABCC7 p.Arg117His P aeruginosa was found in the cultures of more than half of the control children (5 of 9), whereas it was found only once in 1 child who was compound heterozygous for R117H (the colonization by this CF pathogen was detected at the age of 3 in this child and was never found thereafter). Login to comment 81 ABCC7 p.Arg117His It is interesting to note that, in our area, all the patients carrying the R117H variant have been identified exclusively through the CFNS program (ie, the 9 mentioned above who all carried the IVS8-7T allele). Login to comment 83 ABCC7 p.Arg117His TABLE 3 Comparison of the Clinical Characteristics of the 9 R117H Compound Heterozygous Children to Those of the Control Group Cases Controls P Current age, y 7.0 (2.8) 7.1 (3.2) NS Age at the last visit, y 4.5 (3.1) 6.9 (3.2) NS IRT, ␮g/L 1413.3 (374.9) 2038.3 (443.4) .030 IRT, ng/mL 102.3 (49.7) 182.0 (29.7) NS Sweat test (mEq/L) 36.1 (11.3) 96.2 (19.9) Ͻ.001 Meconium ileus, n/N 0/8 0/9 - Pancreatic status (PI), n/N 0/8 9/9 Ͻ.001 Anthropometry Height, z score ϩ0.6 (1.2) -0.1 (1.7) NS Weight, z score ϩ0.2 (1.6) -0.2 (1.7) NS BMI, kg/m2 15.5 (1.5) 15.8 (2.1) NS Pulmonary function FEV1, % 124.3 (11.3) 77.2 (5.8) .051 FVC, % 126.2 (3.5) 86.2 (5.9) .053 IV antibiotic cures, n/N 1/8 3/9 NS Hospitalizations, n/N 0/8 6/9 .009 Complications, n/N 0/8 2/9 NS NS indicates not significant. Login to comment 84 ABCC7 p.Arg117His ABCC7 p.Arg117His patients with CF born in Brittany over a 40-year period (1960-1999).2 By observing these data, we noted that the R117H variant was never observed in the cohort of the 394 patients with CF born before the CFNS protocol enabled the detection of R117H (ie, in 1995) (Fisher`s exact test: P Ͻ .0001). Login to comment 85 ABCC7 p.Arg117His Moreover, to date, no diagnosis of CF has been made in the CF centers of Brittany in patients aged Ն45 years (ie, born before 1960, the first year of our retrospective study) and who carry a genotype including R117H. Login to comment 86 ABCC7 p.Arg117His ABCC7 p.Arg117His DISCUSSION Since our CFNS protocol has enabled the detection of the R117H variant (ie, in 1995), 9 children compound heterozygous for R117H have been detected, which represents 7.3% of the CF children screened in Brittany over this period. Login to comment 87 ABCC7 p.Arg117His R117H was only associated with the 7T form of the IVS8-nT variant and the 11TG sequence of the m(TG) repeat, which does not correspond to the lengths classically observed in the most expressive forms (12 or 13 TG).16 We show here that none of these children have yet developed any signs of CF, the oldest being Ͼ10 years of age. Login to comment 89 ABCC7 p.Arg117His Moreover, no patient bearing a genotype including R117H-7T has yet been diagnosed in adulthood in our area. Login to comment 90 ABCC7 p.Arg117His ABCC7 p.Arg117His However, manifestations of CF lung disease have been reported in some patients bearing R117H on a 7T background in 1 of their 2 CFTR mutated alleles.18,21,22 In 2001, Massie et al18 reported data on a cohort of 38 patients compound heterozygous for R117H who were diagnosed through CFNS or on the basis of clinical signs. Login to comment 91 ABCC7 p.Arg117His Close to 60% of these subjects carried R117H on a 7T background (n ϭ 22). Login to comment 96 ABCC7 p.Arg117His ABCC7 p.Asn1303Lys A recent article reported late diagnosis of CF in 2 elderly men carrying an R117H-7T haplotype heterozygous with either an N1303K or F508del mutation.21 The first patient, aged 61 years, presented with "a 7-month history of progressive weight loss, dyspnea, cough and fever"; his FEV1 and FVC were 60% and 65% of the predicted values, respectively. Login to comment 100 ABCC7 p.Arg117His Another article reported the delayed diagnosis of CF in a 63-year-old woman who carried an F508del/R117H genotype (the IVS8-nT sequence was not known). Login to comment 101 ABCC7 p.Arg117His This woman presented with cough and dyspnea on exertion and was asymptomatic until that time.22 In 2000, Boyne et al20 reported that 3 children screened at birth in the Trent region (United Kingdom) and who were F508del/R117H-7T compound heterozygous already had symptoms of lung disease. Login to comment 103 ABCC7 p.Arg117His Finally, in a recent abstract, Parad et al24 reported that in the CFNS program in Massachusetts and New York, 19 children compound heterozygous for R117H were detected (18 were associated with the 7T variant) and that 3 of them had respiratory symptoms consistent with early CF. Login to comment 105 ABCC7 p.Arg117His In these different reports, it would be important from a genetic point of view to know whether the entire CFTR gene has been analyzed in all these symptomatic patients to ensure the absence of another mutation in cis with the R117H-7T. Login to comment 107 ABCC7 p.Arg117His One can note that description in the literature of compound heterozygous CF patients bearing an R117H-7T haplotype who have progressed toward pulmonary signs of CF remains uncommon and contrast with the high frequency of this haplotype in CFNS programs. Login to comment 109 ABCC7 p.Arg117His The high frequency of the R117H-7T haplotype identified by CFNS programs and the uncertain outcome of these asymptomatic children raise the question of whether this variant should be included in a CFTR mutation panel used for newborn screening. Login to comment 112 ABCC7 p.Arg117His However, does the possible development of such signs in adulthood (perhaps not before the age of 60 years as has e SCOTET et al been reported21,22) justify the formal diagnosis of classical CF at birth, with its consequences in terms of anxiety, possible discrimination for employment or insurance, and so forth?25 In view of these data, we propose the withdrawal of the R117H variant from the panels of CFTR mutations used in newborn screening in light of the expanding implementation of CFNS worldwide. Login to comment 113 ABCC7 p.Arg117His ABCC7 p.Arg117His ABCC7 p.Arg117His The R117H-5T haplotype is more obviously considered to be a disease-causing mutation17; therefore, it is not the overall frequency of the R117H variant that should be considered when deciding whether to include it in panels of mutations, but only the frequency of the R117H-5T haplotype. Login to comment