Comprehensive Study of Microsatellite Instability Testing and Its Comparison With Immunohistochemistry in Gastric Cancers

Purpose@#In this study, polymerase chain reaction (PCR)-based microsatellite instability (MSI) testing was comprehensively analyzed and compared with immunohistochemistry (IHC) for mismatch repair (MMR) protein expression in patients with gastric cancer (GC). @*Materials and Methods@#In 5,676 GC cases, PCR-based MSI testing using five microsatellites (BAT-26, BAT-25, D5S346, D2S123, and D17S250) and IHC for MLH1 were performed. Reevaluation of MSI testing/MLH1 IHC and additional IHC for MSH2, MSH6, and PMS2 were performed in discordant/indeterminate cases. @*Results@#Of the 5,676 cases, microsatellite stable (MSS)/MSI-low and intact MLH1 were observed in 5,082 cases (89.5%), whereas MSI-high (MSI-H) and loss of MLH1 expression were observed in 502 cases (8.8%). We re-evaluated the remaining 92 cases (1.6%) with a discordant/ indeterminate status. Re-evaluation showed 1) 37 concordant cases (0.7%) (18 and 19 cases of MSI-H/MMR-deficient (dMMR) and MSS/MMR-proficient (pMMR), respectively), 2) 6 discordant cases (0.1%) (3 cases each of MSI-H/pMMR and MSS/dMMR), 3) 14 MSI indeterminate cases (0.2%) (1 case of dMMR and 13 cases of pMMR), and 4) 35 IHC indeterminate cases (0.6%) (22 and 13 cases of MSI-H and MSS, respectively). Finally, MSI-H or dMMR was observed in 549 cases (9.7%), of which 47 (0.8%) were additionally confirmed as MSI-H or dMMR by reevaluation. Sensitivity was 99.3% for MSI testing and 95.4% for MMR IHC. @*Conclusions@#Considering the low incidence of MSI-H or dMMR, discordant/indeterminate results were occasionally identified in GCs, in which case complementary testing is required.These findings could help improve the accuracy of MSI/MMR testing in daily practice.

Universal Screening for Lynch Syndrome Compared with Pedigree-Based Screening: 10-Year Experience in a Tertiary Hospital / Journal of the Korean Cancer Association, 대한암학회지

Purpose@#Universal screening for Lynch syndrome (LS) refers to routine tumor testing for microsatellite instability (MSI) among all patients with colorectal cancer (CRC). Despite its widespread adoption, real-world data on the yield is lacking in Korean population. We studied the yield of adopting universal screening for LS in comparison with pedigree-based screening in a tertiary center. @*Materials and Methods@#CRC patients from 2007-2018 were reviewed. Family histories were obtained and were evaluated for hereditary nonpolyposis colorectal cancer (HNPCC) using Amsterdam II criteria. Tumor testing for MSI began in 2007 and genetic testing was offered using all available clinicopathologic data. Yield of genetic testing for LS was compared for each approach and step. @*Results@#Of the 5,520 patients, tumor testing was performed in 4,701 patients (85.2%) and family histories were obtained from 4,241 patients (76.8%). Hereditary CRC (LS or HNPCC) was present in 69 patients (1.3%). MSI-high was present in 6.9%, and 25 patients had confirmed LS. Genetic testing was performed in 41.2% (47/114) of MSI-high patients, out of which 40.4% (19/47) were diagnosed with LS. There were six additional LS patients found outside of tumor testing. For pedigree-based screening, Amsterdam II criteria diagnosed 55 patients with HNPCC. Fifteen of these patients underwent genetic testing, and 11 (73.3%) were diagnosed with LS. Two patients without prior family history were diagnosed with LS and relied solely on tumor testing results. @*Conclusion@#Despite widespread adoption of routine tumor testing for MSI, this is not a fail-safe approach to screen all LS patients. Obtaining a thorough family history in combination with universal screening provides a more comprehensive ‘universal’ screening method for LS.

A Korean case of CTCF related neurodevelopmental disorders

CCCTC-binding factor (CTCF) is a transcriptional regulator that binds to a complex DNA motif in various orientations and plays a crucial role in regulating gene expression, chromatin restructuring, and developmental processes. Mutations in the CTCF are associated with neurodevelopmental disorders. Here we report the first Korean case with a de novo heterozygous variant in the CTCF (c.1025G>A; p.Arg342His). She showed global developmental delay, failure to thrive, and dysmorphic face, which are phenotypes consistent with previous reports in the autosomal dominant intellectual developmental disorder 21 (MIM 615502). She also showed clinical features not previously reported, such as antral web and tracheobronchomalacia.Our case follows suit and expands understanding of this rare disorder by reporting common features and, on the other hand, unreported concomitant congenital anomalies.

Concordance of circulating tumor DNA and matched formalin-fixed paraffin-embedded tumor tissue in gastric cancer as a predictor of recurrence

Purpose@#Combined analysis of the variant composition of circulating tumor DNA (ctDNA) from cell-free plasma and DNA from tumor tissue could provide insight into the implications of the genetic alterations responsible for the intratumoral and intertumoral heterogeneity of gastric cancer. We aimed to evaluate the usefulness of this approach in these patients. @*Methods@#Cell-free plasma and formalin-fixed paraffin-embedded tumor tissue samples from 46 patients with gastric cancer were examined. Targeted deep sequencing was performed using a commercially available kit. @*Results@#The cell-free DNA (cfDNA) concentration was higher in stage II-IV versus stage I patients and in larger versus smaller tumors. Only 12 of the 36 (33.3%) alterations in the tumor tissue samples were in concordance with those in the ctDNA samples. Two variants were in concordance in stage I samples and 10 in stage II-IV samples. Actionable variants that were detected in concordance were in the stage II-IV samples. Preoperative ctDNA positivity of actionable variants was significantly associated with cfDNA concentration, lymphatic invasion, N stage, and TNM stage. Cancer recurrence was significantly associated with tumor size, lymphatic/vascular invasion, TNM stage, and ctDNA-tumor tissue variant concordance. @*Conclusion@#Preoperative ctDNA genetic analysis using a multigene panel offers substantial clinical benefits when performed in conjunction with targeted deep sequencing of tumor tissue. Concordance between preoperative ctDNA and tumor tissue mutations may serve as a prognostic indicator in patients with gastric cancer.

Variant of CHD1 gene resulting in a Korean case of Pilarowski-Bjornsson syndrome

Many monogenic neurodevelopmental disorders have been newly identified in recent years owing to the rapid development of genetic sequencing technology. These include variants of the epigenetic machinery – up to 300 known epigenetic factors of which about 50 have been linked to specific clinical phenotypes. Chromodomain, helicase, DNA binding 1 (CHD1) is an ATP-dependent chromatin remodeler, known to be the causative gene of the autosomal dominant neurodevelopmental disorder Pilarowski-Bjornsson syndrome. Patients exhibit various degrees of global developmental delay, autism, speech apraxia, seizures, growth retardation, and craniofacial dysmorphism. We report the first case of Pilarowski-Bjornsson syndrome in Korea, due to a de novo missense variant of the CHD1 gene (c.862A>G, p.Thr288Ala) in a previously undiagnosed 17-yearold male. His infantile onset of severe global developmental delay, intellectual disability, speech apraxia, and failure to thrive are compatible with Pilarowski-Bjornsson syndrome. We also noted some features not previously reported in this syndrome such as skeletal dysplasia and ichthyosis. Further studies are needed to discover the specific phenotypes and pathogenic mechanisms behind this rare disorder.

Whole Exome Sequencing Identifies Novel Genetic Alterations in Patients with Pheochromocytoma/Paraganglioma

Background@#Pheochromocytoma and paragangliomas (PPGL) are known as tumors with the highest level of heritability, approximately 30% of all cases. Clinical practice guidelines of PPGL recommend genetic testing for germline variants in all patients. In this study, we used whole exome sequencing to identify novel causative variants associated with PPGL to improve the detection of rare genetic variants in our cohort. @*Methods@#Thirty-six tested negative for pathogenic variants in previous Sanger sequencing or targeted gene panel testing for PPGL underwent whole exome sequencing. Whole exome sequencing was performed using DNA samples enriched using TruSeq Custom Enrichment Kit and sequenced with MiSeq (Illumina Inc.). Sequencing alignment and variant calling were performed using SAMtools. @*Results@#Among previously mutation undetected 36 patients, two likely pathogenic variants and 13 variants of uncertain significance (VUS) were detected in 32 pheochromocytoma-related genes. SDHA c.778G>A (p.Gly260Arg) was detected in a patient with head and neck paraganglioma, and KIF1B c.2787-2A>C in a patient with a bladder paraganglioma. Additionally, a likely pathogenic variant in BRCA2, VUS in TP53, and VUS in NFU1 were detected. @*Conclusion@#Exome sequencing further identified genetic alterations by 5.6% in previously mutation undetected patients in PPGL. Implementation of targeted gene sequencing consisted of extended genes of PPGL in routine clinical screening can support the level of comprehensive patient assessment.

Whole Exome Sequencing Identifies Novel Genetic Alterations in Patients with Pheochromocytoma/Paraganglioma

Background@#Pheochromocytoma and paragangliomas (PPGL) are known as tumors with the highest level of heritability, approximately 30% of all cases. Clinical practice guidelines of PPGL recommend genetic testing for germline variants in all patients. In this study, we used whole exome sequencing to identify novel causative variants associated with PPGL to improve the detection of rare genetic variants in our cohort. @*Methods@#Thirty-six tested negative for pathogenic variants in previous Sanger sequencing or targeted gene panel testing for PPGL underwent whole exome sequencing. Whole exome sequencing was performed using DNA samples enriched using TruSeq Custom Enrichment Kit and sequenced with MiSeq (Illumina Inc.). Sequencing alignment and variant calling were performed using SAMtools. @*Results@#Among previously mutation undetected 36 patients, two likely pathogenic variants and 13 variants of uncertain significance (VUS) were detected in 32 pheochromocytoma-related genes. SDHA c.778G>A (p.Gly260Arg) was detected in a patient with head and neck paraganglioma, and KIF1B c.2787-2A>C in a patient with a bladder paraganglioma. Additionally, a likely pathogenic variant in BRCA2, VUS in TP53, and VUS in NFU1 were detected. @*Conclusion@#Exome sequencing further identified genetic alterations by 5.6% in previously mutation undetected patients in PPGL. Implementation of targeted gene sequencing consisted of extended genes of PPGL in routine clinical screening can support the level of comprehensive patient assessment.

Application of Multigene Panel Sequencing in Patients with Prolonged Rate-corrected QT Interval and No Pathogenic Variants Detected in KCNQ1, KCNH2, and SCN5A

Long QT syndrome (LQTS) is an inherited cardiac disease characterized by a prolonged heart rate-corrected QT (QTc) interval. We investigated the genetic causes in patients with prolonged QTc intervals who were negative for pathogenic variants in three major LQTS-related genes (KCNQ1, KCNH2, and SCN5A). Molecular genetic testing was performed using a panel including 13 LQTS-related genes and 67 additional genes implicated in other cardiac diseases. Overall, putative genetic causes of prolonged QTc interval were identified in three of the 30 patients (10%). Among the LQTS-related genes, we detected a previously reported pathogenic variant, CACNA1C c.1552C>T, responsible for cardiac-only Timothy syndrome. Among the genes related to other cardiac diseases, a likely pathogenic variant, RYR2 c.11995A>G, was identified in a patient with catecholaminergic polymorphic ventricular tachycardia. Another patient who developed dilated cardiomyopathy with prolonged QTc interval was found to carry a likely pathogenic variant, TAZ c.718G>A, associated with infantile dilated cardiomyopathy. Comprehensive screening of genetic variants using multigene panel sequencing enables detection of genetic variants with a possible involvement in QTc interval prolongation, thus uncovering unknown molecular mechanisms underlying LQTS.

Spectrum of MNX1 Pathogenic Variants and Associated Clinical Features in Korean Patients with Currarino Syndrome

BACKGROUND: The major genetic cause of Currarino syndrome (CS), a congenital malformation syndrome typically characterized by sacral agenesis, anorectal malformation, and presence of a pre-sacral mass, is known to be pathogenic variants in motor neuron and pancreas homeobox 1 (MNX1), which exist in almost all familial cases and 30% of sporadic cases. Less commonly, a large deletion or a complex rearrangement involving the 7q36 region is associated with CS. We investigated the spectrum of MNX1 pathogenic variants and associated clinical features in the Korean patients with CS. METHODS: We enrolled 25 patients with CS, including 24 sporadic cases and one familial case. Direct sequencing of MNX1 and multiplex ligation-dependent probe amplification were performed. We also analyzed clinical phenotypes and evaluated genotype-phenotype correlations. RESULTS: We identified six novel variants amongst a total of six null variants, one missense variant, and one large deletion. The null variants included four frameshift variants (p.Gly98Alafs*124, p.Gly145Alafs*77, p.Gly151Leufs*67, and p.Ala216Profs*5) and two nonsense variants (p.Tyr186* and p.Gln212*). The missense variant, p.Lys295Gln, was located in the highly-conserved homeobox domain and was predicted to be deleterious. A large deletion involving the 7q36 region was detected in one patient. Pathogenic variants in MNX1 were detected in 28% of all CS cases and 25% of sporadic cases. The clinical phenotype was variable in patients with and without pathogenic variants; no significant genotype-phenotype correlation was observed. CONCLUSIONS: This study revealed the spectrum and phenotypic variability of MNX1 pathogenic variants in the Korean population.

Long-Term Quality Control Program Plan for Cord Blood Banks in Korea: A Pilot Study for Cryopreservation Stability

BACKGROUND: Maintaining the quality of cryopreserved cord blood is crucial. In this pilot study, we describe the results of the internal quality control program for a cord blood bank thus far. METHODS: Donated cord blood units unsuitable for transplantation were selected for internal quality control once a month. One unit of cord blood, aliquoted into 21 capillaries, was cryopreserved and thawed annually to analyze the total nucleated cell count, CD34⁺ cell count, cell viability test, and colony-forming units assay. RESULTS: No significant differences in the variables (total nucleated cell count, cell viability, CD34⁺ cell count) were observed between samples cryopreserved for one and two years. Upon comparing the variables before cryopreservation and post thawing with the capillaries of one year of storage, cell viability and CD34⁺ cell counts decreased significantly. The use of cord blood samples in capillaries, which can be easily stored for a long period, was similar to the methods used for testing segments attached to the cord blood unit. CONCLUSIONS: The results of this study may be useful for determining the period during which the quality of cryopreserved cord blood units used for transplantation is maintained.

Diverse Phenotypic Expression of Cardiomyopathies in a Family with TNNI3 p.Arg145Trp Mutation

Genetic diagnosis of cardiomyopathies is challenging, due to the marked genetic and allelic heterogeneity and the lack of knowledge of the mutations that lead to clinical phenotypes. Here, we present the case of a large family, in which a single TNNI3 mutation caused variable phenotypic expression, ranging from restrictive cardiomyopathy (RCMP) to hypertrophic cardiomyopathy (HCMP) to near-normal phenotype. The proband was a 57-year-old female with HCMP. Examining the family history revealed that her elder sister had expired due to severe RCMP. Using a next-generation sequencing-based gene panel to analyze the proband, we identified a known TNNI3 gene mutation, c.433C>T, which is predicted to cause an amino acid substitution (p.Arg145Trp) in the highly conserved inhibitory region of the cardiac troponin I protein. Sanger sequencing confirmed that six relatives with RCMP or near-normal phenotypes also carried this mutation. To our knowledge, this is the first genetically confirmed family with diverse phenotypic expression of cardiomyopathies in Korea. Our findings demonstrate familial implications, where a single mutation in a sarcomere protein can cause diverse phenotypic expression of cardiomyopathies.

Tumoral Calcinosis as an Initial Complaint of Juvenile-Onset Amyopathic Dermatomyositis

Calcinosis is rarely observed in juvenile-onset amyopathic dermatomyositis in contrast to juvenile-onset dermatomyositis. A 6-year-old female presented with several 0.5 to 2 cm-sized painless grouped masses on both knees for 3 years. The patient also presented with multiple erythematous scaly patches and plaques on both elbows, knuckles, buttock, ankles and cheeks. Her mother had similar skin lesions which were erythematous scaly patches on the knuckles and elbows, since her childhood. When skin biopsy was performed from a left knee nodule, liquid chalky discharge was observed. The biopsy results were consistent with calcinosis cutis. Other biopsies from erythematous patch of the patient and erythematous patch of her mother showed vacuolization of basal cell layer with inflammatory cell infiltrations. Laboratory findings showed normal range of serum phosphorus (4.5 mg/dl), calcium (9.3 mg/dl), 1,25-dihydroxy-vitamin D (10.8 ng/ml) and parathyroid hormone levels (11 pg/ml). Both patient and her mother had no history of muscle weakness and showed normal levels of muscle-specific enzyme. Both patients were diagnosed with juvenile-onset amyopathic dermatomyositis based on histopathology and cutaneous manifestations with no evidence of muscle weakness and no serum muscle enzyme abnormalities. Tumoral calcium deposits observed in daughter was diagnosed as dystrophic calcinosis which can be rarely seen in juvenile-onset amyopathic dermatomyositis. The patient is being treated with oral acetazolamide (40 mg/kg/d) for calcinosis.

Genotyping Influenza Virus by Next-Generation Deep Sequencing in Clinical Specimens

Rapid and accurate identification of an influenza outbreak is essential for patient care and treatment. We describe a next-generation sequencing (NGS)-based, unbiased deep sequencing method in clinical specimens to investigate an influenza outbreak. Nasopharyngeal swabs from patients were collected for molecular epidemiological analysis. Total RNA was sequenced by using the NGS technology as paired-end 250 bp reads. Total of 7 to 12 million reads were obtained. After mapping to the human reference genome, we analyzed the 3-4% of reads that originated from a non-human source. A BLAST search of the contigs reconstructed de novo revealed high sequence similarity with that of the pandemic H1N1 virus. In the phylogenetic analysis, the HA gene of our samples clustered closely with that of A/Senegal/VR785/2010(H1N1), A/Wisconsin/11/2013(H1N1), and A/Korea/01/2009(H1N1), and the NA gene of our samples clustered closely with A/Wisconsin/11/2013(H1N1). This study suggests that NGS-based unbiased sequencing can be effectively applied to investigate molecular characteristics of nosocomial influenza outbreak by using clinical specimens such as nasopharyngeal swabs.

A Case of Myosin-heavy-chain-9 (MYH9) Gene Mutation Confirmed May-Hegglin Anomaly: 11-year Follow-up / 임상소아혈액종양

May-Hegglin anomaly (MHA) is a myosin-heavy-chain-9 (MYH9)-related disorder characterized by thrombocytopenia with giant platelets and inclusion bodies in leukocytes. MHA does not require treatment, but it may be misdiagnosed as immune thrombocytopenic purpura (ITP) and inappropriately managed. Reported herein is a case of a 12 year old female patient diagnosed as MHA with laboratory findings of severe thrombocytopenia and giant platelets in peripheral blood morphology, and followed up until 23 years of age. The patient had been diagnosed with ITP and treated with intravenous gamma-globulin therapy at another hospital, and showed no improvements in platelet count. She was then referred to our hospital for further diagnostic workup and followed up for 11 years, showing platelet count of 6,000-20,000/µL and prolonged platelet function test. She was occasionally treated with iron therapy due to iron-deficiency anemia. In 2014, we conducted a DNA analysis that revealed c.4339G>T(p.Asp1447Tyr), a known mutation of MYH9 gene.

A Case of Myosin-heavy-chain-9 (MYH9) Gene Mutation Confirmed May-Hegglin Anomaly: 11-year Follow-up / 임상소아혈액종양

May-Hegglin anomaly (MHA) is a myosin-heavy-chain-9 (MYH9)-related disorder characterized by thrombocytopenia with giant platelets and inclusion bodies in leukocytes. MHA does not require treatment, but it may be misdiagnosed as immune thrombocytopenic purpura (ITP) and inappropriately managed. Reported herein is a case of a 12 year old female patient diagnosed as MHA with laboratory findings of severe thrombocytopenia and giant platelets in peripheral blood morphology, and followed up until 23 years of age. The patient had been diagnosed with ITP and treated with intravenous gamma-globulin therapy at another hospital, and showed no improvements in platelet count. She was then referred to our hospital for further diagnostic workup and followed up for 11 years, showing platelet count of 6,000-20,000/µL and prolonged platelet function test. She was occasionally treated with iron therapy due to iron-deficiency anemia. In 2014, we conducted a DNA analysis that revealed c.4339G>T(p.Asp1447Tyr), a known mutation of MYH9 gene.

Non-Homologous End Joining Repair Mechanism-Mediated Deletion of CHD7 Gene in a Patient with Typical CHARGE Syndrome

CHARGE syndrome MIM #214800 is an autosomal dominant syndrome involving multiple congenital malformations. Clinical symptoms include coloboma, heart defects, choanal atresia, retardation of growth or development, genital hypoplasia, and ear anomalies or deafness. Mutations in the chromodomain helicase DNA binding protein 7 (CHD7) gene have been found in 65-70% of CHARGE syndrome patients. Here, we describe a 16-month-old boy with typical CHARGE syndrome, who was referred for CHD7 gene analysis. Sequence analysis and multiplex ligation-dependent probe amplification were performed. A heterozygous 38,304-bp deletion encompassing exon 3 with a 4-bp insertion was identified. There were no Alu sequences adjacent to the breakpoints, and no sequence microhomology was observed at the junction. Therefore, this large deletion may have been mediated by non-homologous end joining. The mechanism of the deletion in the current case differs from the previously suggested mechanisms underlying large deletions or complex genomic rearrangements in the CHD7 gene, and this is the first report of CHD7 deletion by this mechanism worldwide.

PRRT2 mutation in Korean patients with paroxysmal kinesigenic dyskinesia: A clinico-genetic analysis

Background & Objective: Recently, mutations in PRRT2 have been found to cause paroxysmal kinesigenic dyskinesia (PKD). However, only several reports have described the detailed clinical features of patients with the PRRT2 mutation compared to those without the mutation. Furthermore, 16p11.2 microdeletions including PRRT2 also have been reported in patients with PKD; however, it is unknown to what extent the PRRT2 deletion contributes to the development of PKD. Methods: We performed mutation screening in 29 Korean patients with PKD analyzing the sequence and gene dosage of PRRT2 and their clinical features. Results: Overall, genetic abnormalities in PRRT2 were identified in 7 patients (24%): 3 from the 6 familial cases (50%) and 4 from the 23 sporadic cases (17%). The previously reported c.649dupC and c.649delC were found in 5 and 1 patient, respectively, and a novel mutation c.323_324delCA was found in 1 patient. No patients had deletions involving the PRRT2 gene. Compared with the mutation-negative cases, the age of PKD onset was earlier in the mutation-positive cases. However, there were no differences in the other clinical features. A dystonia-only phenotype was reported only in the mutation-negative cases. Contrary to common belief that patients with PKD have an excellent response to carbamazepine, 3 mutation-positive patients taking carbamazepine reported only a partial response. Conclusions: PRRT2 is a common causative gene for Korean patients with PKD. Our results show that the incomplete response to carbamazepine does not exclude the PRRT2 mutation.

Evaluation of a Fully Automated, Rapid Detection System for CYP2C19 and UGT1A1 Genotyping / 임상검사와정도관리

BACKGROUND: The need for genotyping single nucleotide polymorphisms (SNPs) in genes encoding drug-metabolizing enzymes is increasing. Therefore, the recent focus has been on developing fully automated methods for the rapid and accurate measurement of SNPs. METHODS: We used the quenching probe (QP) method and i-densy IS-5310 to genotype 200 DNA specimens from 200 healthy Koreans and 100 whole blood from another 100 for the SNPs CYP2C19*2 and CYP2C19*3. We also performed genotyping of UGT1A1*6 and UGT1A1*28 with the above mentioned 200 DNA samples and 81 whole blood samples. The results of the assay were then compared to conventional direct sequencing. RESULTS: The allele frequencies of CYP2C19 were 25.7% for *2 and 10.3% for *3, and those of UGT1A1 were 17.3% for *6 and 11.2% for *28. These results are similar to those reported in previous studies on Korean populations. The CYP2C19 and UGT1A1 genotypes determined by the QP method perfectly matched (100.0%, K=1.000, P<0.001 for CYP2C19, and 99.6%, K=0.992, P<0.001 for UGT1A1) those determined by direct sequencing, barring a single exception for the UGT1A1 genotype in 1 DNA specimen. CONCLUSIONS: Our results suggest that the QP method, owing to its speed and ease of use, will enable rapid and sensitive diagnosis in clinical laboratories.

Identification of a GDF5 Mutation in a Korean Patient with Brachydactyly Type C without Foot Involvement

Brachydactyly type C (BDC) is characterized by shortening of the middle phalanges of the index, middle, and little fingers. Hyperphalangy of the index and middle finger and shortening of the first metacarpal can also be observed. BDC is a rare genetic condition associated with the GDF5 gene, and this condition has not been confirmed by genetic analysis so far in the Korean population. Herein, we present a case of a 6-yr-old girl diagnosed with BDC confirmed by molecular genetic analysis. The patient presented with shortening of the second and third digits of both hands. Sequence analysis of the GDF5 gene was performed and the pathogenic mutation, c.1312C>T (p.Arg438Cys), was identified. Interestingly, this mutation was previously described in a patient who presented with the absence of the middle phalanges in the second through fifth toes. However, our patient showed no involvement of the feet. Considering intrafamilial and interfamilial variability, molecular analysis of isolated brachydactyly is warranted to elucidate the genetic origin and establish a diagnosis.

A Case of Mycobacterium marinum Infection Diagnosed by PCR Amplification and Direct Sequencing / 대한피부과학회지

Mycobacterium marinum is an atypical mycobacterium (ATM) and is an uncommon cause of skin and soft tissue infections associated with contact with contaminated water. Diagnosis is often delayed when only a conventional identification method is used. PCR amplification and direct sequencing is recently available method for rapid identification of ATM. We report a case of M. marinum infection identified by PCR and sequencing. A 56-year-old female was referred for multiple erythematous nodules on both forearms which appeared two months ago. Skin biopsy showed suppurative granulomatous inflammation, and AFB culture showed nontuberculous Mycobacteria. PCR and sequencing were performed, and the obtained sequences were compared to the database using BLAST. The sequences of 16S rRNA and rpoB could not differentiate between M. marinum and M. ulcerans, showing 100% homology to both. Identification was possible using the sequences of the tuf and hsp65 genes, showing both 100% homology to M. marinum, while 99.8%, 99.7% to M. ulcerans. The patient was treated with clarithromycin, rifampicin, and ethambutol for 6 months.