A very rare presentation of mitochondrial elongation factor Tu deficiency-TUFM mutation and literature review.

OBJECTIVES: The mitochondrial elongation factor Tu (EF-Tu), encoded by the TUFM gene, is a GTPase, which is part of the mitochondrial protein translation mechanism. If it is activated, it delivers the aminoacyl-tRNAs to the mitochondrial ribosome. Here, a patient was described with a homozygous missense variant in the TUFM [c.1016G>A (p.Arg339Gln)] gene. To date, only six patients have been reported with bi-allelic pathogenic variants in TUFM, leading to combined oxidative phosphorylation deficiency 4 (COXPD4) characterized by severe early-onset lactic acidosis, encephalopathy, and cardiomyopathy. CASE PRESENTATION: The patient presented here had the phenotypic features of TUFM-related disease, lactic acidosis, hypotonia, liver dysfunction, optic atrophy, and mild encephalopathy. CONCLUSIONS: We aimed to expand the clinical spectrum of pathogenic variants of TUFM.

A possibly new autoinflammatory disease due to compound heterozygous phosphomevalonate kinase gene mutation.

BACKGROUND: Mevalonate kinase (MVK) plays a role in cholesterol and non-sterol isoprenoid biosynthesis and its deficiency-related diseases are caused by bi-allelic pathogenic mutations in the MVK gene, (MVK), which leads to rare hereditary autoinflammatory diseases. The disease may manifest different clinical phenotypes depending on the degree of the deficiency in the enzyme activity. The complete deficiency of the enzyme activity results in the severe metabolic disease called mevalonic aciduria, while a partial deficiency results in a broad spectrum of clinical presentations called hyper-immunoglobulin D syndrome (HIDS). Serum immunoglobulin (Ig) D and urine mevalonic acid levels may be increased during inflammatory attacks of HIDS. CASE PRESENTATION: Herein, for the first time in the literature, we present a 6-year-old male patient who suffered from recurrent episodes of fever, polyarthritis, skin rash, diarrhea, abdominal pain, and inflammatory bowel disease-like manifestations with elevated levels of serum IgD, and urine mevalonic acid. Eventually we detected compound heterozygous mutations in the phosphomevalonate kinase (PMVK) gene coding the second enzyme after mevalonate kinase in the mevalonate pathway. CONCLUSION: For patients presenting with HIDS-like findings, disease exacerbations and persistent chronic inflammation, and having high urinary mevalonic acid and serum IgD levels, raising suspicion in terms of MVK deficiency (MVKD), it is recommended to study all mevalonate pathway enzymes, even if there is no mutation in the MVK gene. It should be kept in mind that novel mutations might be seen such as PMVK gene.

Expected or unexpected clinical findings in liver glycogen storage disease type IX: distinct clinical and molecular variability.

OBJECTIVES: To reveal the different clinical presentations of liver glycogen storage disease type IX (GSD IX), which is a clinically and genetically heterogeneous type of glycogenosis. METHODS: The data from the electronic hospital records of 25 patients diagnosed with liver GSD IX was reviewed. Symptoms, clinical findings, and laboratory and molecular analysis were assessed. RESULTS: Of the patients, 10 had complaints of short stature in the initial presentation additionally other clinical findings. Elevated serum transaminases were found in 20 patients, and hepatomegaly was found in 22 patients. Interestingly, three patients were referred due to neurodevelopmental delay and hypotonia, while one was referred for only autism. One patient who presented with neurodevelopmental delay developed hepatomegaly and elevated transaminases during the disease later on. Three of the patients had low hemoglobin A1C and fructosamine values that were near the lowest reference range. Two patients had left ventricular hypertrophy. Three patients developed osteopenia during follow-up, and one patient had osteoporosis after puberty. The most common gene variant, PHKA2, was observed in 16 patients, 10 variants were novel and six variants were defined before. Six patients had variants in PHKG2, two variants were not defined before and four variants were defined before. PHKB variants were found in three patients. One patient had two novel splice site mutations in trans position. It was revealed that one novel homozygous variant and one defined homozygous variant were found in PHKB. CONCLUSIONS: This study revealed that GSD IX may present with only hypotonia and neurodevelopmental delay without liver involvement in the early infantile period. It should be emphasized that although liver GSDIX is thought of as a benign disease, it might present with multisystemic involvement and patients should be screened with echocardiography, bone mineral densitometry, and psychometric evaluation.

Two patients from Turkey with a novel variant in the GM2A gene and review of the literature.

OBJECTIVES: GM2 gangliosidosis is a rare form of inborn errors of metabolism including Tay-Sachs disease, Sandhoff disease, and GM2 activator deficiency. GM2 activator protein deficiency is an ultra-rare form of GM2 gangliosidosis. To date, 16 cases of GM2 activator protein deficiency have been reported in the literature, and among them, 11 cases were the infantile form of the disease. Here we report the first two patients from Turkey with the infantile form of the disease with a novel likely pathogenic variant. CASE PRESENTATION: A boy of eight months old presented to the metabolic department with very mild neurological deterioration, although he had achieved early developmental milestones at the appropriate time. The parents also had a daughter who had lost skills progressively before one year of age. The boy was evaluated and bilateral cherry-red spots were found with no abnormality in either metabolic screening including ß-hexosaminidase or cranial magnetic resonance imaging. A novel homozygous likely pathogenic variant in GM2A was detected in a next-generation sequence panel revealing GM2 activator protein deficiency. His sister was investigated after he was diagnosed with GM2 activator deficiency and it was found that she had the same variant as her brother. CONCLUSIONS: This case report emphasizes that in the event of normal ß-hexosaminidase activity, GM2 activator protein deficiency could be underdiagnosed, and further molecular analysis should be performed. To the best of our knowledge, this boy is one of the youngest patient diagnosed with very mild symptoms. With this novel pathogenic variant, these patients have expanded the mutation spectrum of GM2 activator protein deficiency.

The first case with FBXL4 mutation successfully treated with a parenteral ketogenic diet for lactic acidosis.

BACKGROUND: The ketogenic diet (KD) is a low-carbohydrate, high-fat diet that has been used as an effective nonpharmacological treatment in many neurological and metabolic disorders for a long time. The effectiveness of the KD is revealed in mitochondrial disorders, mainly in pyruvate dehydrogenase deficiency. CASE REPORT: A 4-year-old girl who was diagnosed with an F-box and leucine-rich repeat protein 4 (FBXL4) gene mutation was hospitalized with sepsis. She was first given standard parenteral nutrition (PN) because of gastrointestinal problems. During the disease course, lactic acidosis became prominent and did not respond to pharmacological treatment; standard PN was gradually switched to parenteral KD, and lactate levels decreased after parenteral KD. The patient was discharged with an enteral KD. CONCLUSION: This is the first case of mitochondrial depletion syndrome effectively treated with parenteral KD for lactic acidosis.

Hypophosphatasia: is it an underdiagnosed disease even by expert physicians?

INTRODUCTION: Hypophosphatasia (HPP) is caused by mutations in the ALPL that encodes the tissue-nonspecific isoenzyme of alkaline phosphatase (ALP). Clinical manifestations range from extreme life-threatening lethal forms to no signs or symptoms at all. MATERIALS AND METHODS: Consecutive 30,000 outpatients and inpatients with ALP data were screened retrospectively, out of which 1000 patients were found to have low levels of ALP more than once. Then, patients were evaluated for the symptoms and signs of HPP with further biochemical and genetic analyses. RESULTS: Thirty-seven patients who had severe musculoskeletal pain, recurrent fractures, and tooth anomalies were then screened with substrate and DNA sequencing analyses for HPP. It was determined that eight patients had variants in the ALPL gene. A total of eight different ALPL variants were identified in eight patients. The variants, namely c.244G > C (p.Gly82Arg), c.1444C > T (p.His482Tyr), c.1487A > G (p.Asn493Ser), and c.675_676insCA (p.Met226GlnfsTer52), had not been previously reported. DISCUSSION: Considering the wide spectrum of clinical signs and symptoms, HPP should be among the differential lists of bone, muscle, and tooth abnormalities at any age.

Evaluation of monocyte to HDL cholesterol ratio and other inflammatory markers in patients with psoriasis

Abstract Background Psoriasis is a chronic systemic inflammatory disease frequently associated with serious comorbidities. Objectives To investigate the systemic inflammatory burden in psoriasis and to assess the correlation between traditional and novel inflammatory markers and the severity of the disease. Methods This cross-sectional study was conducted on 60 patients with psoriasis vulgaris and 50 healthy volunteers. Data including demographics, Psoriasis Area and Severity Index scores, and laboratory results were analyzed and compared. Results Compared with the control group, the psoriatic patients had significantly higher high sensitive C-reactive protein, serum amyloid A, erythrocyte sedimentation rate, leukocyte, neutrophil, neutrophil-to-lymphocyte ratio, monocyte to high density lipoprotein (HDL) cholesterol ratio, and aspartate aminotransferase levels, and significantly lower HDL cholesterol levels (p < 0.05). No significant difference was found in procalcitonin, lymphocyte, monocyte, hemoglobin, red blood cell distribution width, platelet, mean platelet volume, platelet distribution width, lymphocyte-to-monocyte ratio, anti-cyclic citrullinated peptide, glucose, alanine aminotransaminase, blood urea nitrogen, creatinine, triglyceride, total cholesterol, and LDL cholesterol levels between the two groups (p > 0.05). The Psoriasis Area and Severity Index score was positively correlated with high-sensitivity C-reactive protein, serum amyloid A, and monocyte to HDL cholesterol ratio, and negatively correlated with lymphocyte-to-monocyte ratio (p < 0.05). Study limitations This was a single-center study with relatively limited numbers of patients and controls. Conclusions The data show that high sensitivity C-reactive protein, serum amyloid A, erythrocyte sedimentation rate, neutrophil-to-lymphocyte ratio, and monocyte to HDL cholesterol ratio can be used as markers of systemic inflammation in patients with psoriasis. Moreover, high sensitivity C-reactive protein, serum amyloid A, monocyte to HDL cholesterol ratio and lymphocyte-to-monocyte ratio are closely related to the Psoriasis Area and Severity Index score, and they may be regarded as objective indicators in determining the disease severity.

Evaluation of monocyte to HDL cholesterol ratio and other inflammatory markers in patients with psoriasis.

BACKGROUND: Psoriasis is a chronic systemic inflammatory disease frequently associated with serious comorbidities. OBJECTIVES: To investigate the systemic inflammatory burden in psoriasis and to assess the correlation between traditional and novel inflammatory markers and the severity of the disease. METHODS: This cross-sectional study was conducted on 60 patients with psoriasis vulgaris and 50 healthy volunteers. Data including demographics, Psoriasis Area and Severity Index scores, and laboratory results were analyzed and compared. RESULTS: Compared with the control group, the psoriatic patients had significantly higher high sensitive C-reactive protein, serum amyloid A, erythrocyte sedimentation rate, leukocyte, neutrophil, neutrophil-to-lymphocyte ratio, monocyte to high density lipoprotein (HDL) cholesterol ratio, and aspartate aminotransferase levels, and significantly lower HDL cholesterol levels (p < 0.05). No significant difference was found in procalcitonin, lymphocyte, monocyte, hemoglobin, red blood cell distribution width, platelet, mean platelet volume, platelet distribution width, lymphocyte-to-monocyte ratio, anti-cyclic citrullinated peptide, glucose, alanine aminotransaminase, blood urea nitrogen, creatinine, triglyceride, total cholesterol, and LDL cholesterol levels between the two groups (p > 0.05). The Psoriasis Area and Severity Index score was positively correlated with high-sensitivity C-reactive protein, serum amyloid A, and monocyte to HDL cholesterol ratio, and negatively correlated with lymphocyte-to-monocyte ratio (p < 0.05). STUDY LIMITATIONS: This was a single-center study with relatively limited numbers of patients and controls. CONCLUSIONS: The data show that high sensitivity C-reactive protein, serum amyloid A, erythrocyte sedimentation rate, neutrophil-to-lymphocyte ratio, and monocyte to HDL cholesterol ratio can be used as markers of systemic inflammation in patients with psoriasis. Moreover, high sensitivity C-reactive protein, serum amyloid A, monocyte to HDL cholesterol ratio and lymphocyte-to-monocyte ratio are closely related to the Psoriasis Area and Severity Index score, and they may be regarded as objective indicators in determining the disease severity.

Evaluation of interleukin-23 receptor (IL-23R) gene polymorphisms and serum IL-23 levels in patients with psoriasis

Background/aim: IL-23R gene polymorphisms and the association of these polymorphisms with serum IL-23 levels were investigated in patients with psoriasis in the current study. Materials and methods: Sixty-seven patients with psoriasis who were admitted to our dermatology outpatient clinic and 67 healthy controls were included in the study. Polymorphisms of the IL-23R gene were determined by KASP-PCR method, and serum IL-23 levels were determined by ELISA method. Results: The distribution of IL-23R gene polymorphisms rs2201841, rs11209026, rs7530511, rs1343152, and rs11465804 was not significantly different in the patient and control groups. The AA genotype of the rs2201841 locus in males and the GA genotype in females, as well as the AA genotype of the rs1343152 locus in males and the CA genotype in females, were statistically significant in patients with psoriasis. The mean serum IL-23 level was significantly lower in the patient group (42.62 ± 5.96) compared to the control groups (75.76 ± 13.24). Conclusion: IL-23R gene polymorphisms including rs2201841, rs11209026, rs7530511, rs11465804, and rs1343152 were not found to be significantly related to psoriasis. Different genetic polymorphisms may play a role in the development of psoriasis in female and male populations. Ethnic differences between different populations may have led to differences in the distribution of polymorphisms in the current study with compared to other published studies. Additionally, many different genes, polymorphisms, and environmental factors that have an effect on the development of psoriasis may affect the disease process.

Dysfunction of GRAP, encoding the GRB2-related adaptor protein, is linked to sensorineural hearing loss.

We have identified a GRAP variant (c.311A>T; p.Gln104Leu) cosegregating with autosomal recessive nonsyndromic deafness in two unrelated families. GRAP encodes a member of the highly conserved growth factor receptor-bound protein 2 (GRB2)/Sem-5/drk family of proteins, which are involved in Ras signaling; however, the function of the growth factor receptor-bound protein 2 (GRB2)-related adaptor protein (GRAP) in the auditory system is not known. Here, we show that, in mouse, Grap is expressed in the inner ear and the protein localizes to the neuronal fibers innervating cochlear and utricular auditory hair cells. Downstream of receptor kinase (drk), the Drosophila homolog of human GRAP, is expressed in Johnston's organ (JO), the fly hearing organ, and the loss of drk in JO causes scolopidium abnormalities. drk mutant flies present deficits in negative geotaxis behavior, which can be suppressed by human wild-type but not mutant GRAP. Furthermore, drk specifically colocalizes with synapsin at synapses, suggesting a potential role of such adaptor proteins in regulating actin cytoskeleton dynamics in the nervous system. Our findings establish a causative link between GRAP mutation and nonsyndromic deafness and suggest a function of GRAP/drk in hearing.

Identification of candidate gene FAM183A and novel pathogenic variants in known genes: High genetic heterogeneity for autosomal recessive intellectual disability.

The etiology of intellectual disability (ID) is heterogeneous including a variety of genetic and environmental causes. Historically, most research has not focused on autosomal recessive ID (ARID), which is a significant cause of ID, particularly in areas where parental consanguinity is common. Identification of genetic causes allows for precision diagnosis and improved genetic counseling. We performed whole exome sequencing to 21 Turkish families, seven multiplex and 14 simplex, with nonsyndromic ID. Based on the presence of multiple affected siblings born to unaffected parents and/or shared ancestry, we consider all families as ARID. We revealed the underlying causative variants in seven families in MCPH1 (c.427dupA, p.T143Nfs*5), WDR62 (c.3406C>T, p.R1136*), ASPM (c.5219_5225delGAGGATA, p.R1740Tfs*7), RARS (c.1588A>G, p.T530A), CC2D1A (c.811delG, p.A271Pfs*30), TUSC3 (c.793C>T, p.Q265*) and ZNF335 (c.808C>T, p.R270C and c.3715C>A, p.Q1239K) previously linked with ARID. Besides ARID genes, in one family, affected male siblings were hemizygous for PQBP1 (c.459_462delAGAG, p.R153Sfs*41) and in one family the proband was female and heterozygous for X-chromosomal SLC9A6 (c.1631+1G>A) variant. Each of these variants, except for those in MCPH1 and PQBP1, have not been previously published. Additionally in one family, two affected children were homozygous for the c.377G>A (p.W126*) variant in the FAM183A, a gene not previously associated with ARID. No causative variants were found in the remaining 11 families. A wide variety of variants explain half of families with ARID. FAM183A is a promising novel candidate gene for ARID.

Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation.

RIPOR2 (previously known as FAM65B) localizes to stereocilia of auditory hair cells and causes deafness when its function is disturbed by mutations. Here, we demonstrate that during the morphogenesis of the hair cell bundle, absence of Ripor2 affects the orientation of this key subcellular structure. We show that Ripor2 interacts with Myh9, a protein encoded by a known deafness gene. Absence of Ripor2 is associated with low Myh9 abundance in the mouse cochlea despite increased amount of Myh9 transcripts. While Myh9 is mainly expressed in stereocilia, a phosphorylated form of Myh9 is particularly enriched in the kinocilium. In Ripor2-deficient mice, kinocilium shows an aberrant localization which associates with a reduced content of phosphorylated Myh9. Acetylated alpha tubulin, another specific kinociliary protein which contributes to microtubule stabilization, is reduced in the absence of Ripor2 as well. We propose that Ripor2 deficiency influences abundance and/or post-translational modifications of proteins expressed in both stereocilia and kinocilia. This effect may have a negative impact on the structure and function of the auditory hair cell bundle.

Monosomy chromosome 21 compensated by 21q22.11q22.3 duplication in a case with small size and minor anomalies.

BACKGROUND: Partial monosomy 21 is a rare finding with variable sizes and deletion breakpoints, presenting with a broad spectrum of phenotypes. CASE PRESENTATION: We report a 10-month-old boy with short stature, minor anomalies and mild motor delay. The patient had a monosomy 21 and duplication of the 21q22.11q22.3 region on the remaining derivative chromosome 21 which represents a partial 21q uniparental disomy of paternal origin, upd(21q22.11q22.3)pat. The abnormalities were characterized by karyotyping, FISH, chromosomal microarray, and genotyping. CONCLUSIONS: This is the first case showing a monosomy 21 compensated by upd(21q22.11q22.3) as a mechanism of genomic rescue. Because there is no strong evidence showing imprinting on chromosome 21, the uniparental disomy itself is not associated with abnormal phenotype but has reduced phenotype severity of monosomy 21. We reviewed the previously published cases with isolated 21q deletions and identified a common deletion of 5.7 Mb associated with low birth weight, length and head circumference in the 21q21.2 region.

Novel pathogenic variants underlie SLC26A4-related hearing loss in a multiethnic cohort.

OBJECTIVES: The genetics of sensorineural hearing loss is characterized by a high degree of heterogeneity. Despite this heterogeneity, DNA variants found within SLC26A4 have been reported to be the second most common contributor after those of GJB2 in many populations. METHODS: Whole exome sequencing and/or Sanger sequencing of SLC26A4 in 117 individuals with sensorineural hearing loss with or without inner ear anomalies but not with goiter from Turkey, Iran, and Mexico were performed. RESULTS: We identified 27 unique SLC26A4 variants in 31 probands. The variants c.1673A > G (p.N558S), c.1708-1G > A, c.1952C > T (p.P651L), and c.2090-1G > A have not been previously reported. The p.N558S variant was detected in two unrelated Mexican families. CONCLUSION: A range of SLC26A4 variants without a common recurrent mutation underlies SLC26A4-related hearing loss in Turkey, Iran, and Mexico.

Novel EYA1 variants causing Branchio-oto-renal syndrome.

INTRODUCTION: Branchio-oto-renal (BOR) syndrome is an autosomal dominant genetic disorder characterized by second branchial arch anomalies, hearing impairment, and renal malformations. Pathogenic mutations have been discovered in several genes such as EYA1, SIX5, and SIX1. However, nearly half of those affected reveal no pathogenic variant by traditional genetic testing. METHODS AND MATERIALS: Whole Exome sequencing and/or Sanger sequencing performed in 10 unrelated families from Turkey, Iran, Ecuador, and USA with BOR syndrome in this study. RESULTS: We identified causative DNA variants in six families including novel c.525delT, c.979T > C, and c.1768delG and a previously reported c.1779A > T variants in EYA1. Two large heterozygous deletions involving EYA1 were detected in additional two families. Whole exome sequencing did not reveal a causative variant in the remaining four families. CONCLUSIONS: A variety of DNA changes including large deletions underlie BOR syndrome in different populations, which can be detected with comprehensive genetic testing.

Dominant deafness-onychodystrophy syndrome caused by an ATP6V1B2 mutation.

Our report clarifies the role of ATP6V1B2 in patients with deafness and onycho-osteodystrophy and confirms that a recurring ATP6V1B2 c.1516C>T [p.(Arg506*)], variant causes dominant deafness-onychodystrophy (DDOD) syndrome.

Audiological findings in Noonan syndrome.

OBJECTIVES: The aim of this study was to evaluate audiologic properties of patients with Noonan syndrome and compare these findings with those of unaffected peers. METHODS: The study included 17 children with Noonan syndrome and 20 typically developing children without Noonan syndrome. Pure tone and speech audiometry, immitancemetric measurement, otoacoustic emissions measurement and auditory brainstem response tests were applied to all (n = 37) children. RESULTS: Hearing thresholds of children with Noonan syndrome were higher (poorer) than those observed unaffected peers, while the hearing sensitivity of the both groups were normal limits (p = 0.013 for right, p = 0.031 for left ear). Transient evoked otoacoustic emissions amplitudes of the children with Noonan syndrome were lower than the children without Noonan syndrome (p = 0.005 for right, p = 0.002 for left ear). Middle ear pressures and auditory brainstem response values were within normal limits and there was no difference between the two groups (p > 0.05). CONCLUSION: General benefit of the present study is to characterize the audiologic findings of children with Noonan syndrome, which is beneficial in clinics evaluating children with Noonan syndrome.

HPSE2 mutations in urofacial syndrome, non-neurogenic neurogenic bladder and lower urinary tract dysfunction.

BACKGROUND: Urofacial syndrome (UFS) is characterised by congenital bladder dysfunction accompanied by a characteristic abnormal grimace upon smiling and crying. In recent years, biallelic mutations of HPSE2 and LRIG2 have been reported in UFS patients. Non-neurogenic neurogenic bladder (NNNB) has a bladder identical to UFS without typical facial features. The aim of this study was to analyse HPSE2 mutations in patients with UFS and NNNB or severe lower urinary tract dysfunction (LUTD) without abnormal facial expression. METHODS: Patients with UFS, NNNB and severe LUTD were enrolled in the study. We examined a total of 35 patients from 33 families. There were seven UFS patients from five different families, 21 patients with NNNB and seven with LUTD. HPSE2 gene mutation analysis was performed using the polymerase chain reaction protocol followed by Sanger sequencing in these patients. RESULTS: A twin pair with UFS was found to be homozygous for c.457C>T (p.Arg153*) mutation. No other pathogenetic variant was detected. CONCLUSION: HPSE2 mutations were found in one UFS family but not detected in patients with NNNB and severe LUTD. Considering the increasingly recognised cases of NNNB that were diagnosed in early childhood period, genetic factors appear to be responsible. Thus, further genetic studies are needed to discover novel associated gene variants in these bladder anomalies.

Identification of copy number variants through whole-exome sequencing in autosomal recessive nonsyndromic hearing loss.

Genetic variants account for more than half of the cases with congenital or prelingual onset hearing loss. Autosomal recessive nonsyndromic hearing loss (ARNSHL) is the most common subgroup. Whole-exome sequencing (WES) has been shown to be effective detecting deafness-causing single-nucleotide variants (SNVs) and insertion/deletions (INDELs). After analyzing the WES data for causative SNVs or INDELs involving previously reported deafness genes in 78 families with ARNSHL, we searched for copy number variants (CNVs) through two different tools in 24 families that remained unresolved. We detected large homozygous deletions in STRC and OTOA in single families. Thus, causative CNVs in known deafness genes explain 2 out of 78 (2.6%) families in our sample set. We conclude that CNVs can be reliably detected through WES and should be the part of pipelines used to clarify genetic basis of hearing loss.

Whole-exome sequencing efficiently detects rare mutations in autosomal recessive nonsyndromic hearing loss.

Identification of the pathogenic mutations underlying autosomal recessive nonsyndromic hearing loss (ARNSHL) is difficult, since causative mutations in 39 different genes have so far been reported. After excluding mutations in the most common ARNSHL gene, GJB2, via Sanger sequencing, we performed whole-exome sequencing (WES) in 30 individuals from 20 unrelated multiplex consanguineous families with ARNSHL. Agilent SureSelect Human All Exon 50 Mb kits and an Illumina Hiseq2000 instrument were used. An average of 93%, 84% and 73% of bases were covered to 1X, 10X and 20X within the ARNSHL-related coding RefSeq exons, respectively. Uncovered regions with WES included those that are not targeted by the exome capture kit and regions with high GC content. Twelve homozygous mutations in known deafness genes, of which eight are novel, were identified in 12 families: MYO15A-p.Q1425X, -p.S1481P, -p.A1551D; LOXHD1-p.R1494X, -p.E955X; GIPC3-p.H170N; ILDR1-p.Q274X; MYO7A-p.G2163S; TECTA-p.Y1737C; TMC1-p.S530X; TMPRSS3-p.F13Lfs*10; TRIOBP-p.R785Sfs*50. Each mutation was within a homozygous run documented via WES. Sanger sequencing confirmed co-segregation of the mutation with deafness in each family. Four rare heterozygous variants, predicted to be pathogenic, in known deafness genes were detected in 12 families where homozygous causative variants were already identified. Six heterozygous variants that had similar characteristics to those abovementioned variants were present in 15 ethnically-matched individuals with normal hearing. Our results show that rare causative mutations in known ARNSHL genes can be reliably identified via WES. The excess of heterozygous variants should be considered during search for causative mutations in ARNSHL genes, especially in small-sized families.