Common mutations of familial hypercholesterolemia patients in Taiwan: characteristics and implications of migrations from southeast China

Familial hypercholesterolemia (FH) is an autosomal dominant disease caused by mutations in low-density lipoprotein receptor (LDLR), apolipoprotein B-100 (APOB), and proprotein convertase subtilisin/kexin type 9 (PCSK9) genes. This study investigated FH patients carrying common mutations in Taiwan and compared them to FH southeastern Asians. Causal FH mutations were identified by exon-by-exon sequencing with/without multiplex ligation-dependent probe amplification among 208 Taiwanese with clinically diagnosed FH. Haplotype analyses among probands and family members were undertaken using TaqMan® Assays. Totally, LDLR mutations were found in 118 probands, consisting of 61 different loci, and APOB 10579C>T mutations in 12 probands. Three mutations (64delG, 1661C>T, and 2099A>G) were novel. LDLR 986G>A (13.1%), 1747C>T (10.8%), and APOB 10579C>T (9.2%) were common mutations with no differences in phenotypes. LDLR 1747C>T associated with one haplotype (CAAGCCCCATGG/(dTA)n-112nt); LDLR 986G>A with two. APOB 10579C>T associated with the same LDLR binding-domain pattern in Taiwanese and southeastern Asians. We concluded that LDLR 986G>A, 1747C>T and APOB 10579C>T are common mutations, with combined frequency of approximately 33%. The presence of different haplotypes associated with FH common mutations in Taiwan indicates multiple historical migrations, probable multiple recurrent origins from southern China, and haplotype homologies reflect the presence of common ancestors in southern China.     

Genetic Polymorphisms in LDLR,APOB, PCSK9 and Other Lipid Related Genes Associated with Familial Hypercholesterolemia in Malaysia

Familial hypercholesterolemia (FH) is an autosomal dominant disorder characterized by elevations in total cholesterol (TC) and low density lipoprotein cholesterol (LDLc). Development of FH can result in the increase of risk for premature cardiovascular diseases (CVD). FH is primarily caused by genetic variations in Low Density Lipoprotein Receptor (LDLR), Apolipoprotein B (APOB) or Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) genes. Although FH has been extensively studied in the Caucasian population, there are limited reports of FH mutations in the Asian population. We investigated the association of previously reported genetic variants that are involved in lipid regulation in our study cohort. A total of 1536 polymorphisms previously implicated in FH were evaluated in 141 consecutive patients with clinical FH (defined by the Dutch Lipid Clinic Network criteria) and 111 unrelated control subjects without FH using high throughput microarray genotyping platform. Fourteen Single Nucleotide Polymorphisms (SNPs) were found to be significantly associated with FH, eleven with increased FH risk and three with decreased FH risk. Of the eleven SNPs associated with an increased risk of FH, only one SNP was found in the LDLR gene, seven in the APOB gene and three in the PCSK9 gene. SNP rs12720762 in APOB gene is associated with the highest risk of FH (odds ratio 14.78, p<0.001). Amongst the FH cases, 108 out of 141 (76.60%) have had at least one significant risk-associated SNP. Our study adds new information and knowledge on the genetic polymorphisms amongst Asians with FH, which may serve as potential markers in risk prediction and disease management.     

Genetic Testing of Korean Familial Hypercholesterolemia Using Whole-Exome Sequencing

Familial hypercholesterolemia (FH) is a genetic disorder with an increased risk of early-onset coronary artery disease. Although some clinically diagnosed FH cases are caused by mutations in LDLR, APOB, or PCSK9, mutation detection rates and profiles can vary across ethnic groups. In this study, we aimed to provide insight into the spectrum of FH-causing mutations in Koreans. Among 136 patients referred for FH, 69 who met Simon Broome criteria with definite family history were enrolled. By whole-exome sequencing (WES) analysis, we confirmed that the 3 known FH-related genes accounted for genetic causes in 23 patients (33.3%). A substantial portion of the mutations (19 of 23 patients, 82.6%) resulted from 17 mutations and 2 copy number deletions in LDLR gene. Two mutations each in the APOB and PCSK9 genes were verified. Of these anomalies, two frameshift deletions in LDLR and one mutation in PCSK9 were identified as novel causative mutations. In particular, one novel mutation and copy number deletion were validated by co-segregation in their relatives. This study confirmed the utility of genetic diagnosis of FH through WES.     

Molecular characterization of Polish patients with familial hypercholesterolemia: novel and recurrentLDLR mutations

Autosomal dominant hypercholesterolemia (ADH) is caused by mutations in the genes coding for the low-density lipoprotein receptor (LDLR), apolipoprotein B-100 (APOB), or proprotein convertase subtilisin/kexin type 9 (PCSK9). In this study, a molecular analysis ofLDLR andAPOB was performed in a group of 378 unrelated ADH patients, to explore the mutation spectrum that causes hypercholesterolemia in Poland. All patients were clinically diagnosed with ADH according to a uniform protocol and internationally accepted WHO criteria. Mutational analysis included all exons, exon-intron boundaries and the promoter sequence of theLDLR, and a fragment of exon 26 ofAPOB. Additionally, the MLPA technique was applied to detect rearrangements withinLDLR. In total, 100 sequence variations were identified in 234 (62%) patients. WithinLDLR, 40 novel and 59 previously described sequence variations were detected. Of the 99LDLR sequence variations, 71 may be pathogenic mutations. The most frequentLDLR alteration was a point mutation p.G592E detected in 38 (10%) patients, followed by duplication of exons 4–8 found in 16 individuals (4.2%). Twenty-five cases (6.6%) demonstrated the p.R3527Q mutation ofAPOB. Our findings imply that major rearrangements of theLDLR gene as well as 2 point mutations (p.G592E inLDLR and p.R3527Q inAPOB) are frequent causes of ADH in Poland. However, the heterogeneity ofLDLR mutations detected in the studied group confirms the requirement for complex molecular studies of Polish ADH patients.     

Familial hypercholesterolemia in St. Petersburg: Diversity of mutations argues against a strong founder effect

Examination of low-density lipoprotein (LDL) receptor gene, its promoter, and most of exon-intron boundaries from 74 probands with familial hypercholesterolemia (FH) of St. Petersburg revealed 34 mutations and 8 widely spread polymorphisms at this locus. Only four mutations were considered neutral, while the other 30 are likely to cause familial hypercholesterolemia (FH). Mutations in the LDL receptor gene, causing the disease, were identified in 41 (55%) out of 74 families with FH. Mutation R3500Q in apolipoprotein B (APOB) gene was not detected in all probands. Therefore in the families lacking mutations hypercholesterolemia was caused by mutations in the introns of the LDL receptor gene or by other genetic factors. Nineteen mutations causing disease progression were described in St. Petersburg for the first time, while 18 of them are specific for Russia. Among Ashkenazi Jews, predominant mutation G197del was detected in 30% (7 out of 22) of patients with FH. In the Slavic population of St. Petersburg, no predominant mutations were detected. Only five mutations were identified in two Slavic families, while 24 were found in unique families. These data are indicative of the lack of a strong founder effect for FH in the St. Petersburg population.     

Use of Targeted Exome Sequencing in Genetic Diagnosis of Chinese Familial Hypercholesterolemia

Familial hypercholesterolemia is an autosomal dominant inherited disease characterized by elevated plasma low-density lipoprotein cholesterol (LDL-C). It is mainly caused by mutations of the low-density lipoprotein receptor (LDLR) gene. Currently, the methods of whole genome sequencing or whole exome sequencing for screening mutations in familial hypercholesterolemia are not applicable in China due to high cost. We performed targeted exome sequencing of 167 genes implicated in the homozygous phenotype of a proband pedigree to identify candidate mutations, validated them in the family of the proband, studied the functions of the mutant protein, and followed up serum lipid levels after treatment. We discovered that exon 9 c.1268 T>C and exon 8 c.1129 T>G compound heterozygous mutations in the LDLR gene in the proband derived from the mother and father, respectively, in which the mutation of c.1129 T>G has not been reported previously. The mutant LDL-R protein had 57% and 52% binding and internalization functions, respectively, compared with that of the wild type. After 6 months of therapy, the LDL-C level of the proband decreased by more than 50% and the LDL-C of the other family members with heterozygous mutation also reduced to normal. Targeted exome sequencing is an effective method for screening mutation genes in familial hypercholesterolemia. The exon 8 and 9 mutations of the LDLR gene were pedigree mutations. The functions of the mutant LDL-R protein were decreased significantly compared with that of the wild type. Simvastatin plus ezetimibe was proven safe and effective in this preschool-age child.     

Lifelong reduction of LDL-cholesterol related to a common variant in the LDL-receptor gene decreases the risk of coronary artery disease--a Mendelian Randomisation study

Background

Rare mutations of the low-density lipoprotein receptor gene (LDLR) cause familial hypercholesterolemia, which increases the risk for coronary artery disease (CAD). Less is known about the implications of common genetic variation in the LDLR gene regarding the variability of cholesterol levels and risk of CAD.

Methods

Imputed genotype data at the LDLR locus on 1 644 individuals of a population-based sample were explored for association with LDL-C level. Replication of association with LDL-C level was sought for the most significant single nucleotide polymorphism (SNP) within the LDLR gene in three European samples comprising 6 642 adults and 533 children. Association of this SNP with CAD was examined in six case-control studies involving more than 15 000 individuals.

Findings

Each copy of the minor T allele of SNP rs2228671 within LDLR (frequency 11%) was related to a decrease of LDL-C levels by 0.19 mmol/L (95% confidence interval (CI) [0.13–0.24] mmol/L, p = 1.5×10⁻¹⁰). This association with LDL-C was uniformly found in children, men, and women of all samples studied. In parallel, the T allele of rs2228671 was associated with a significantly lower risk of CAD (Odds Ratio per copy of the T allele: 0.82, 95% CI [0.76–0.89], p = 2.1×10⁻⁷). Adjustment for LDL-C levels by logistic regression or Mendelian Randomisation models abolished the significant association between rs2228671 with CAD completely, indicating a functional link between the genetic variant at the LDLR gene locus, change in LDL-C and risk of CAD.

Conclusion

A common variant at the LDLR gene locus affects LDL-C levels and, thereby, the risk for CAD.     

贵州省1例家族性高胆固醇血症家系基因突变筛查与评估

摘要 目的：探讨贵州省1例家族性高胆固醇血症（FH）家系基因突变筛查与评估结果。方法：参照荷兰脂质诊断网络（DLCN）指南诊断标准于2021年11月-2022年11月贵阳市某三甲医院选取1例临床诊断FH的患者进行研究,分析其家系系谱,采用C8000型全自动生化分析仪检测家系成员总胆固醇（TC）、甘油三酯（TG）、LDL-C、高密度脂蛋白胆固醇（HDL-C）水平;并采集家系临床相关数据,收集血清样本提取白细胞DNA进行全基因组外显子测序致病基因,筛选出4个FH相关基因[低密度脂蛋白受体（LDLR）、载脂蛋白B（ApoB）、西布曲明9a型（PCSK9）、LDLR衔接蛋白1（LDLRAP1）]的单核苷酸多态性（SNP）位点情况,采用Polyphen-2和SIFT软件对SNP位点进行致病性分析;同时回顾性分析双重滤过血浆置换(DFPP)吸附治疗期间的心血管疾病发生情况及治疗前后的载脂蛋白A（ApoA）、载脂蛋白E（ApoE）、载脂蛋白B（ApoB）、脂蛋白a（LPa）、TC、TG、HDL-C、LDL-C、游离脂肪酸（FFA）水平变化情况。结果：该家系Ⅰ-1成员血清LDL-C达8.16 mmol/L,Ⅱ-1成员血清LDL-C达7.0 mmol/L,Ⅱ-2成员血清LDL-C达3.45 mmol/L,按照DLCN标准,Ⅰ-1评7分,Ⅱ-1评6分,均提示患FH可能性大,达到FH临床诊断标准。利用Polyphen-2预测,该家系ApoB基因中rs676210、rs679899分别得分0.999、0.998,1个新位点c.10094A＞T得分为0.829,均提示可能致病,SIFT软件预测以上三个位点均有害。DFPP治疗后患者病情稳定,至今无心绞痛严重心血管事件发生。与吸附治疗前比较,吸附治疗后ApoA、ApoE、ApoB、LPa、TG、HDL-C、LDL-C、TC水平较低FFA水平较高,差异有统计学意义（P＜0.05）。结论：ApoB基因SNP位点突变很可能是该家系引起FH的主要原因,而DFPP治疗有利于调节FH患者血脂水平,进而降低心血管疾病的发生风险。     

Angptl4 deficiency decreases serum triglyceride levels in low-density lipoprotein receptor knockout mice and streptozotocin-induced diabetic mice

Angiopoietin-like protein family 4 (Angptl4) has been shown to regulate lipoprotein metabolism through the inhibition of lipoprotein lipase (LPL). In familial hypercholesterolemia (FH), individuals lacking low-density lipoprotein receptor (LDLR) present not only hypercholesterolemia, but also increased plasma triglyceride (TG)-rich lipoprotein remnants, and develop atherosclerosis. In addition, the most common type of dyslipidemia in individuals with diabetes is increased TG levels.We first generated LDLR^−/−Angptl4^−/− mice to study the effect of Angptl4 deficiency on the lipid metabolism. Fasting total cholesterol, VLDL-C, LDL-C, HDL-C and TG levels were decreased in LDLR^−/−Angptl4^−/− mice compared with LDLR^−/−Angptl4^+/+ mice. In particular, post olive oil-loaded TG excursion were largely attenuated in LDLR^−/−Angptl4^−/− mice compared with LDLR^−/−Angptl4^+/+ mice. We next introduced diabetes by streptozotocin (STZ) treatment in Angptl4^−/− mice and examined the impacts of Angptl4 deficiency. Compared with diabetic Angptl4^+/+ mice, diabetic Angptl4^−/− mice showed the improvement of fasting and postprandial hypertriglyceridemia as well. Thus, targeted silencing of Angptl4 offers a potential therapeutic strategy for the treatment of dyslipidemia in individuals with FH and insulin deficient diabetes.     

TaqIB polymorphism in the CETP gene modulates the impact of HC/LF diet on the HDL profile in healthy Chinese young adults

The aim of this study was to investigate the interactions of genetic variants in the genes of cholesterol ester transfer protein (CETP) and low-density lipoprotein receptor (LDLR) with high carbohydrate and low fat (HC/LF) diet on lipid profiles in a young and healthy Chinese Han population. Fifty-six healthy subjects (22.89±1.80 years) were given washout diets of 31% fat and 54% carbohydrate for 7 days, followed by HC/LF diets of 15% fat and 70% carbohydrate for 6 days, with no total energy restriction. Serum lipid profiles at baseline, after washout and following HC/LF diets, as well as CETP and LDLR polymorphisms were analyzed. Carriers of B2 allele of CETP TaqIB polymorphism had significantly higher levels of high density lipoprotein cholesterol (HDL-C) and apo A-I in the whole study population after the diet intervention. Notably, males with CETP TaqIB B1B1 experienced significantly increased HDL-C and apo A-I after HC/LF diet. Regarding the LDLR Pvu II polymorphism, both P1P1 subjects and P2 carriers experienced decreased total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels after HC/LF diet with no statistically significant differences between the genotypes. Our results demonstrate that the elevated HDL-C levels after HC/LF diet in healthy Chinese Han youth are associated with CETP TaqI B2 allele while males with B1B1 genotype are more susceptible to the influence of HC/LF diet on their HDL-C levels. The decreased TC and LDL-C levels after HC/LF diet are not associated with LDLR Pvu II polymorphism.     

Expression of Recombinant LDLR–EGFP Fusion Protein in HEK-293 Cells as a Promising Tool to Assess the Effect of <Emphasis Type="Italic">LDLR</Emphasis> Gene Mutations

Mutations in the low density lipoprotein receptor gene (LDLR) frequently impair folding and intracellular traffic of the receptor protein, resulting in the development of a monogenic disorder, familial hypercholesterolemia (FH). Identification of novel LDLR mutations requires confirmation of their functional importance in distinguishing pathogenic mutations from neutral changes in the aminoacid sequence. To elaborate a system for evaluation of the effect of mutation on the folding and intracellular transport of the LDLR, as well as its ability to bind low density lipoprotein (LDL), we constructed a plasmid containing LDLR cDNA and the gene of enhanced green fluorescent protein (EGFP). Confocal microscopy has shown that, upon transient transfection of HEK293 cells with the plasmid, the recombinant fusion protein LDLR–EGFP is transported onto the cellular membrane and binds labeled LDL. This construct will be further modified by site-directed mutagenesis to reproduce the LDLR missense mutations most common in the population of northwest Russia so as to study the subcellular localization and function of the modified chimeric protein.     

青少年家族性高胆固醇血症患者血浆同型半胱氨酸和高敏C 反应蛋白水 平的临床价值及与血脂相关性研究

目的:探讨血浆同型半胱氨酸(Homocysteine,Hcy)、高敏C反应蛋白(Hypersensitive C-reactive protein,hs-CRP)在家族性高胆固醇血症(FH)的纯合子和杂合子患者中的水平及其与临床生化指标的相关性。方法:入选在2013.10~2015.7期间在动脉硬化门诊随访、确诊的家族性高胆固醇患者34人(纯合子14例,杂合子20例)。根据FH纯合子、杂合子、健康体检者分成三组,分别测定其总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)、空腹血糖(Glu)、Hcy、hs-CRP水平,并比较FH患者血浆LDL-C、非高密度脂蛋白(non-HDL)水平Hcy、hs-CRP水平的相关性。结果:FH组的TC、LDL-C、non-HDL、Hcy水平显著高于正常对照组(P0.05)。FH根据基因型亚组分析中,青少年纯合子组HDL-C[(0.78±0.21)vs(1.25±0.40)mmol/L]小于杂合子组(P0.001),而TC[(16.11±2.66)vs(7.30±2.54)mmol/L]、LDL-C[(14.06±2.22)vs(5.25±2.16)mmol/L]、non-HDL[(15.33±2.60)vs(6.05±2.61)mmol/L]、Hcy[(19.3±11.58)vs(11.29±3.42)μmol/L]水平显著高于杂合子组(P0.05)。Pearson相关性分析显示,FH患者血浆LDL-C、non-HDL水平与Hcy水平呈正相关(P0.05),而与hs-CRP无相关性。结论:FH患者,特别是青少年的纯合子患者,与对照组相较,具有较高的TC、LDL-C和Hcy水平,并且与血浆LDL-C、non-HDL水平呈正相关。FH患者hs-CRP的水平高于健康人,但差异无统计学意义,与血浆LDL-C、non-HDL水平也无明显相关性。     

A combined LDL receptor/LDL receptor adaptor protein 1 mutation as the cause for severe familial hypercholesterolemia

Familial hypercholesterolemia (FH) results from impaired catabolism of plasma low density lipoproteins (LDL), thus leading to high cholesterol, atherosclerosis, and a high risk of premature myocardial infarction. FH is commonly caused by defects of the LDL receptor or its main ligand apoB, together mediating cellular uptake and clearance of plasma LDL. In some cases FH is inherited by mutations in the genes of PCSK9 and LDLRAP1 (ARH) in a dominant or recessive trait. The encoded proteins are required for LDL receptor stability and internalization within the LDLR pathway. To detect the underlying genetic defect in a family of Turkish descent showing unregular inheritance of severe FH, we screened the four candidate genes by denaturing gradient gel electrophoresis (DGGE) mutation analysis. We identified different combinatory mixtures of LDLR- and LDLRAP1-gene defects as the cause for severe familial hypercholesterolemia in this family. We also show for the first time that a heterozygous LDLR mutation combined with a homozygous LDLRAP1 mutation produces a more severe hypercholesterolemia phenotype in the same family than a homozygous LDLR mutation alone.     

Estimation of the prevalence of familial hypercholesterolaemia in a rural Afrikaner community by direct screening for three Afrikaner founder low density lipoprotein receptor gene mutations

We have determined the prevalence of familial hypercholesterolaemia (FH) in a rural Afrikaner community by means of direct DNA screening for three founder-related Afrikaner low density lipoprotein (LDL) receptor gene mutations. A random sample of 1612 persons, aged 15–64 years, was selected as a subsample of 4583 subjects from an Afrikaner community living in the south-western Cape, South Africa. Participants who had a total serum cholesterol (TC) in the high TC category as defined in the consensus recommendations by the Southern African Heart Foundation, were screened for three founder-related LDL receptor gene mutations, causing FH in 90% of Afrikaners. Of the subsample, 201 participants (12.5%) had TC levels above the 80th percentile. In this group the combined prevalence of the three common Afrikaner LDL receptor gene defects (D206E, FH Afrikaner-1; V408M, FH Afrikaner-2; D154N, FH Afrikaner-3) was calculated as 1 : 83. When taking into account the reported background prevalence of other FH gene defects of 1 : 500 in this community, their overall prevalence of FH was estimated to be 1 : 72. The significant differences found between the FH patients and other high risk patients with raised cholesterol levels were higher TC and LDL cholesterol levels and lower high density lipoprotein cholesterol levels in FH patients. The treatment status of the molecularly identified FH patients and other hypercholesterolaemic persons suggests that this condition is inadequately diagnosed and poorly managed in this study population. An extrapolation to the entire South African population suggests that there are about 112 000 FH patients in the country who are underdiagnosed as a group and therefore not receiving the care that would help to reduce the burden of FH-associated ischaemic heart disease in South Africa. Received: 30 November 1995 / Revised: 15 March 1996     

Recurrent and novel LDL receptor gene mutations causing heterozygous familial hypercholesterolemia in La Habana

The molecular basis of familial hypercholesterolemia (FH) in three families of Spanish descent from La Habana was investigated by the candidate gene approach. The Arg3500Gln mutation of apolipoprotein B-100 was not found. Identification of low density lipoprotein receptor (LDLR) gene haplotypes segregating with FH guided the characterisation of three point mutations by automated sequencing. One, a Val408Met missense mutation, a founder mutation in Afrikaner FH patients, was recurrent, being associated with a distinct DNA haplotype. The other two, Glu256Lys and Val776Met missense mutations, were novel and modified highly conserved residues. These mutations were absent in normolipidemic subjects and were associated in heterozygous carriers with twice the cholesterol levels observed in noncarriers. Noticeably, cardiovascular complications were rarely observed in older heterozygotes, even in those with the Afrikaner FH-2 mutation. These findings confirm the molecular heterogeneity of LDLR gene mutations causing FH and the variability of their expression across different populations.     

Two mutations in LDLR gene were found in two Chinese families with familial hypercholesterolemia

Familial hypercholesterolemia (FH) (OMIM 143890) is an autosomal dominantly inherited disease mainly caused by mutations of the gene encoding the low density lipoprotein receptor (LDLR) and Apolipoprotein (Apo) B. First the common mutation R3500Q in ApoB gene was determined using PCR/RFLP method. Then the LDLR gene was screened for mutations using Touch-down PCR, SSCP and sequencing techniques. Furthermore, the secondary structure of the LDLR protein was predicted with ANTHEPROT5.0. The R3500Q mutation was absent in these two families. A heterozygous p.W483X mutation of LDLR gene was identified in family A which caused a premature stop codon, while a homozygous mutation p.A627T was found in family B. The predicted secondary structures of the mutant LDLR were altered. We identified two known mutations (p.W483X, p.A627T) of the LDLR gene in two Chinese FH families respectively.     

Autosomal Dominant Hypercholesterolemia: Needs for Early Diagnosis and Cascade Screening in the Tunisian Population

Autosomal dominant hypercholesterolemia (ADH) is characterized by an isolated elevation of plasmatic low-density lipoprotein (LDL), which predisposes to premature coronary artery disease (CAD) and early death. ADH is largely due to mutations in the low-density lipoprotein receptor gene (LDLR), the apolipoprotein B-100 gene (APOB), or the proprotein convertase subtilisin/kexin type 9 (PCSK9). Early diagnosis and initiation of treatment can modify the disease progression and its outcomes. Therefore, cascade screening protocol with a combination of plasmatic lipid measurements and DNA testing is used to identify relatives of index cases with a clinical diagnosis of ADH. In Tunisia, an attenuated phenotypic expression of ADH was previously reported, indicating that the establishment of a special screening protocol is necessary for this population.     

The c.42_52del11 Mutation in TPRN and Progressive Hearing Loss in a Family from Pakistan

The DFNB79 locus harbors TPRN mutations in which have been reported in a few families with deafness. Four frameshift mutations in TPRN have been described to cause severe or severe-to-profound hearing loss in Moroccan and Pakistani families, and a single frameshift mutation was associated with progressive hearing loss in deaf individuals in a Dutch family. We identified a Pakistani family in which the affected individuals were homozygous for a pathogenic mutation, c.42_52del11, in TPRN (p.G15Afs150X). In contrast to the previously reported individuals affected by the same mutation, hearing loss is likely to be progressive in this family. Thus the same mutation of TPRN can be associated with different thresholds of hearing as well as differences in the stability of the phenotype.