A Novel Heterozygous Missense Variant (c.667G>T;p.Gly223Cys) in USH1C That Interferes With Cadherin-Related 23 and Harmonin Interaction Causes Autosomal Dominant Nonsyndromic Hearing Loss

BACKGROUND: Pathogenic variants of USH1C, encoding a PDZ-domain-containing protein called harmonin, have been known to cause autosomal recessive syndromic or nonsyndromic hearing loss (NSHL). We identified a causative gene in a large Korean family with NSHL showing a typical pattern of autosomal dominant (AD) inheritance.METHODS: Exome sequencing was performed for five affected and three unaffected individuals in this family. Following identification of a candidate gene variant, segregation analysis and functional studies, including circular dichroism and biolayer interferometry experiments, were performed.RESULTS: A novel USH1C heterozygous missense variant (c.667G>T;p.Gly223Cys) was shown to segregate with the NSHL phenotype in this family. This variant affects an amino acid residue located in the highly conserved carboxylate-binding loop of the harmonin PDZ2 domain and is predicted to disturb the interaction with cadherin-related 23 (cdh23). The affinity of the variant PDZ2 domain for a biotinylated synthetic peptide containing the PDZ-binding motif of cdh23 was approximately 16-fold lower than that of the wild-type PDZ2 domain and that this inaccessibility of the binding site was caused by a conformational change in the variant PDZ2 domain.CONCLUSIONS: A heterozygous variant of USH1C that interferes with the interaction between cdh23 and harmonin causes novel AD-NSHL.

First Molecular Diagnosis of a Patient with Unverricht-Lundborg Disease in Korea

Unverricht-Lundborg disease (ULD) is a form of progressive myoclonus epilepsy characterized by stimulation-induced myoclonus and seizures. This disease is an autosomal recessive disorder, and the gene CSTB, which encodes cystatin B, a cysteine protease inhibitor, is the only gene known to be associated with ULD. Although the prevalence of ULD is higher in the Baltic region of Europe and the Mediterranean, sporadic cases have occasionally been diagnosed worldwide. The patient described in the current report showed only abnormally enlarged restriction fragments of 62 dodecamer repeats, confirming ULD, that were transmitted from both her father and mother who carried the abnormally enlarged restriction fragment as heterozygotes with normal-sized fragments. We report the first case of a genetically confirmed patient with ULD in Korea.

Novel 4-bp Intronic Deletion (c.1560+3_1560+6del) in LEMD3 in a Korean Patient With Osteopoikilosis

Osteopoikilosis is an autosomal dominant bone disorder characterized by symmetric multiple osteosclerotic lesions throughout the axial and appendicular skeleton. Pathogenic variants in the LEMD3 have been identified as the cause of osteopoikilosis. LEMD3 encodes an inner nuclear membrane protein that interacts with bone morphogenetic protein (BMP) and transforming growth factor (TGF)-β pathways. We report the case of a 19-year-old man presenting with lower back pain and sciatica. His radiograph revealed bilateral and symmetrical multiple osteosclerotic bone lesions in both scapular areas. Sanger sequencing of LEMD3 revealed a four-base-pair deletion in intron 2 (c.1560+3_1560+6del), which was inherited from his father. We found that this four-base-pair deletion in intron 2 causes aberrant splicing and consequent deletion of exon 2. To the best of our knowledge, this is the first report of genetically confirmed osteopoikilosis in Korea.

Bilateral Simple Ectopia Lentis Associated with FBN1 Gene Mutation

PURPOSE: To report a case of bilateral simple ectopia lentis associated with FBN1 gene mutation. CASE SUMMARY: A 47-year-old women presented with a one-month history of ocular pain and decreased visual acuity of the right eye. She had a family history of crystalline lens dislocation but showed no systemic abnormality or trauma history. Intraocular pressure was 45 mmHg in the right eye, which showed a myopic shift (−6.5 D). The crystalline lens of the right eye was subluxated to the anterior chamber, and the angle was closed. Phacoemulsification with scleral fixation of the posterior chamber intraocular lens of the right eye was performed. After that, best corrected visual acuity of the right eye was 1.0, and intraocular pressure was 15 mmHg. After 2 years, she presented with intermittent ocular pain and decreased visual acuity of the left eye. The crystalline lens of the left eye was subluxated to the anterior chamber. Phacoemulsification with scleral fixation of the posterior chamber intraocular lens of the left eye was performed. After that, intermittent ocular pain and visual acuity of the left eye were improved. Genetic testing confirmed an FBN1 gene mutation in the patient. CONCLUSIONS: A bilateral ectopia lentis patient without history of definite trauma should undergo complete systemic and ophthalmic examination to rule out accompanying disease, and a detailed family history should be collected. If hereditary ectopia lentis is suspected, genetic testing of probands and their family should be performed and will be helpful for genetic counseling and ophthalmic surveillance.

First Report of Familial Dysalbuminemic Hyperthyroxinemia With an ALB Variant

Familial dysalbuminemic hyperthyroxinemia (FDH) is an inherited disease characterized by increased circulating total thyroxine (T4) levels and normal physiological thyroid function. Heterozygous albumin gene (ALB) variants have been reported to be the underlying cause of FDH. To our knowledge, there have been no confirmed FDH cases in Korea. We recently observed a female patient with mild T4 elevation (1.2 to 1.4-fold) and variable levels of free T4 according to different assay methods. Upon Sanger sequencing of her ALB, a heterozygous c.725G>A (p.Arg242His) variant was identified. The patient's father and eldest son had similar thyroid function test results and were confirmed to have the same variant. Although the prevalence of FDH might be very low in the Korean population, clinical suspicion is important to avoid unnecessary evaluation and treatment.

Identification of Pathogenic Variants in the CHM Gene in Two Korean Patients With Choroideremia

Choroideremia is a rare X-linked disorder causing progressive chorioretinal atrophy. Affected patients develop night blindness with progressive peripheral vision loss and eventual blindness. Herein, we report two Korean families with choroideremia. Multimodal imaging studies showed that the probands had progressive loss of visual field with characteristic chorioretinal atrophy, while electroretinography demonstrated nearly extinguished cone and rod responses compatible with choroideremia. Sanger sequencing of all coding exons and flanking intronic regions of the CHM gene revealed a novel small deletion at a splice site (c.184_189+3delTACCAGGTA) in one patient and a deletion of the entire exon 9 in the other. This is the first report on a molecular genetic diagnosis of choroideremia in Korean individuals. Molecular diagnosis of choroideremia should be widely adopted for proper diagnosis and the development of new treatment modalities including gene therapy.

A Case of Antley-Bixler Syndrome With a Novel Likely Pathogenic Variant (c.529G>C) in the POR Gene

No abstract available.

Clinical Characteristics of Marfan Syndrome in Korea

BACKGROUND AND OBJECTIVES: Marfan syndrome (MFS) is a connective tissue disorder with autosomal dominant inheritance and a highly variable clinical spectrum. However, there are limited data available on the clinical features of Korean patients with MFS. The aim of the present study was to describe the clinical characteristics and outcomes of Korean patients with MFS. SUBJECTS AND METHODS: We included all patients who were diagnosed with MFS between January 1995 and May 2015 at a single tertiary medical center. Patients with an MFS-related disorder including MASS phenotype (myopia, mitral valve prolapse, borderline and non-progressive aortic root dilatation, skeletal findings, and striae), mitral valve prolapse syndrome, and ectopia lentis syndrome were excluded. A total of 343 Korean patients aged ≥15 years who satisfied the revised Ghent nosology were included. RESULTS: The mean patient age at diagnosis was 35.9±12.6 years and 172 (50.1%) patients were male. Median follow-up duration was 52.8 months. A total of 303 patients (88.6%) had aortic root dilatation with Z score ≥2 or aortic root dissection. Ectopia lentis was relatively less common (163 patients, 55.1%) and systemic score ≥7 was found in 217 patients (73.8%). Among 219 probands, a family history of MFS was present in 97 patients (44.5%) and sporadic cases in 121 patients (55.5%). Among the 157 probands who underwent genetic analysis, 141 (89.8%) had an FBN1 mutation associated with aortic root aneurysm/dissection. Aortic dissection (AD) or intramural hematoma (IMH) was identified in 110 patients (32.1%). Among the 221 patients without AD or IMH, descending aortic aneurysms were identified in 19 patients (8.6%). Two hundred thirteen patients (62%) underwent cardiovascular surgery of any type. Eight patients died during follow-up. CONCLUSION: We described the clinical characteristics and outcomes of Korean MFS patients. Cardiovascular manifestations were commonly detected and FBN1 mutation was present in approximately 90% of patients. In contrast, ectopia lentis was identified in approximately half of patients. Our findings will be informative for the evaluation of patients with MFS.

Clinical Characteristics and Genotype-Phenotype Correlation of Korean Patients with Spinal and Bulbar Muscular Atrophy

PURPOSE: Spinal and bulbar muscular atrophy (SBMA) is an X-linked motor neuron disease characterized by proximal muscle weakness, muscle atrophy, and fasciculation. Although SBMA is not uncommon in Korea, there is only one study reporting clinical characteristics and genotype-phenotype correlation in Korean patients. MATERIALS AND METHODS: In this study, age at the onset of symptoms, the score of severity assessed by impairment of activities of daily living milestones, and rate of disease progression, and their correlations with the number of CAG repeats in the androgen receptor (AR) gene, as well as possible correlations among clinical characteristics, were analyzed in 40 SBMA patients. RESULTS: The median ages at onset and at diagnosis were 44.5 and 52.5 years, respectively, and median interval between onset and diagnosis and median rate of disease progression were 5.0 years and 0.23 score/year, respectively. The median number of CAG repeats in the AR gene was 44 and the number of CAG repeats showed a significant inverse correlation with the age at onset of symptoms (r=-0.407, p=0.009). In addition, patients with early symptom onset had slower rate of disease progression. CONCLUSION: As a report with the largest and recent Korean cohort, this study demonstrates clinical features of Korean patients with SBMA and reaffirms the inverse correlation between the age at disease onset and the number of CAG repeats. Interestingly, this study shows a possibility that the rate of disease progression may be influenced by the age at onset of symptoms.

Mutation Analysis of the TGFBI Gene in Consecutive Korean Patients With Corneal Dystrophies

BACKGROUND: Mutations in the transforming growth factor beta-induced gene (TGFBI) are major causes of genetic corneal dystrophies (CDs), which can be grouped into TGFBI CDs. Although a few studies have reported the clinical and genetic features of Korean patients with TGFBI CD, no data are available regarding the frequency and spectrum of TGFBI mutations in a consecutive series of Korean patients with clinically diagnosed CDs. METHODS: Patients with any type of CD, who underwent both ophthalmologic examination and TGFBI gene analysis by Sanger sequencing at a tertiary care hospital in Seoul, Korea from 2006 to 2013, were enrolled in this study. RESULTS: Among a total of 89 patients, 77 (86.5%) were diagnosed as having clinical TGFBI CD. Seventy-three out of 74 patients (98.6%) with granular CD type 2 (GCD2), had the p.R124H mutation. Of particular note, one patient with rapidly progressive CD had the p.R124H mutation as well as a novel nonsense variant with unknown clinical significance (p.A179*). In three patients with lattice CD type 1 (LCD1), one known mutation (p.R124C) and two novel variants (p.L569Q and p.T621P) in the TGFBI gene were identified. CONCLUSIONS: This study provides epidemiological insight into CDs in a Korean population and reaffirms that GCD2 is the most common TGFBI CD phenotype and that p.R124H is the only mutation identified in patients with GCD2. In addition, we broaden the spectrum of TGFBI mutations by identifying two novel missense variants in patients with LCD1.

Identification of Somatic KRAS Mutation in a Korean Baby with Nevus Sebaceus Syndrome

No abstract available.

Significance of Myositis Autoantibody in Patients with Idiopathic Interstitial Lung Disease

PURPOSE: Some patients with interstitial lung disease (ILD) related to connective tissue disease (CTD) have a delayed diagnosis of the underlying CTD when the ILD is categorized as idiopathic. In this study, we evaluated the frequency of myositis autoantibodies in patients diagnosed with idiopathic ILD and investigated the clinical significance stemming from the presence of the antibodies. MATERIALS AND METHODS: A total 32 patients diagnosed with idiopathic ILD were enrolled in this study. We analyzed a panel of 11 myositis autoantibody specificities in the patients using a line blot immunoassay. Then, we divided them into myositis autoantibody-positive and -negative groups and compared the clinical features and laboratory data between the two groups. RESULTS: Of the 32 idiopathic ILD patients, 12 patients had myositis autoantibodies encompassing 9 specificities, except for anti-Mi-2 and anti-PM-Scl 100 (12/32, 38%). Anti-synthetase autoantibodies including Jo-1, EJ, OJ, PL-7, and PL-12 were present in 7 patients (7/32, 22%). The group with myositis autoantibodies presented more frequently with the symptom of mechanic's hand and showed abnormal pulmonary function test results with low forced vital capacity, diffusing capacity for carbon monoxide, total lung capacity, and high lactate dehydrogenase values in blood when compared with the group without myositis antibodies. CONCLUSION: We strongly suggest that patients undergo an evaluation of myositis autoantibodies, if they are diagnosed with idiopathic ILD in the presence of clinical characteristics including mechanic's hand, arthralgia, and autoantibodies which are insufficient to make a diagnosis of a specific CTD category.

Absence of HLA-B*1502 and HLA-A*3101 Alleles in 9 Korean Patients With Antiepileptic Drug-Induced Skin Rash: A Preliminary Study

There have been a number of studies about correlations between HLA genotypes in various ethnic groups and occurrence of various cutaneous adverse drug reactions, ranging in intensity from mild to severe, caused by antiepileptic drugs (AEDs). This is the first report analyzing the HLA genotypes of 9 Korean patients with skin rashes induced by various AEDs. The AEDs that induced skin rash were lamotrigine (n=3), carbamazepine (n=3), oxcarbazepine (n=1), phenobarbital (n=1), and phenytoin (n=1). None of the patients' HLA genotypes was either HLA-B*1502 or HLA-A*3101. Based on these series of cases, AED-induced skin rash can occur independently of HLA-B*1502 or HLA-A*3101 genotypes in the Korean patients.

A Cryptic ETV6/ABL1 Rearrangement Represents a Unique Fluorescence In Situ Hybridization Signal Pattern in a Patient with B Acute Lymphoblastic Leukemia

No abstract available.