Somatic uniparental disomy mitigates the most damaging EFL1 allele combination in Shwachman-Diamond syndrome.

Shwachman-Diamond syndrome (SDS; OMIM #260400) is caused by variants in SBDS (Shwachman-Bodian-Diamond syndrome gene), which encodes a protein that plays an important role in ribosome assembly. Recent reports suggest that recessive variants in EFL1 are also responsible for SDS. However, the precise genetic mechanism that leads to EFL1-induced SDS remains incompletely understood. Here we present 3 unrelated Korean SDS patients who carry biallelic pathogenic variants in EFL1 with biased allele frequencies, resulting from a bone marrow-specific somatic uniparental disomy in chromosome 15. The recombination events generated cells that were homozygous for the relatively milder variant, allowing for the evasion of catastrophic physiologic consequences. However, the milder EFL1 variant was still solely able to impair 80S ribosome assembly and induce SDS features in cell line and animal models. The loss of EFL1 resulted in a pronounced inhibition of terminal oligopyrimidine element-containing ribosomal protein transcript 80S assembly. Therefore, we propose a more accurate pathogenesis mechanism of EFL1 dysfunction that eventually leads to aberrant translational control and ribosomopathy.

Biallelic novel mutations of the COL27A1 gene in a patient with Steel syndrome.

An 11-year-old Korean boy presented with short stature, hip dysplasia, radial head dislocation, carpal coalition, genu valgum, and fixed patellar dislocation and was clinically diagnosed with Steel syndrome. Scrutinizing the trio whole-exome sequencing data revealed novel compound heterozygous mutations of COL27A1 (c.[4229_4233dup]; [3718_5436del], p.[Gly1412Argfs*157];[Gly1240_Lys1812del]) in the proband, which were inherited from heterozygous parents. The maternal mutation was a large deletion encompassing exons 38-60, which was challenging to detect.

Novel RPL13 Variants and Variable Clinical Expressivity in a Human Ribosomopathy With Spondyloepimetaphyseal Dysplasia.

Spondyloepimetaphyseal dysplasias (SEMDs) are a heterogeneous group of disorders with variable growth failure and skeletal impairments affecting the spine and long bone epiphyses and metaphyses. Here we report on four unrelated families with SEMD in which we identified two monoallelic missense variants and one monoallelic splice site variant in RPL13, encoding the ribosomal protein eL13. In two out of four families, we observed autosomal dominant inheritance with incomplete penetrance and variable clinical expressivity; the phenotypes of the mutation-positive subjects ranged from normal height with or without hip dysplasia to severe SEMD with severe short stature and marked skeletal dysplasia. In vitro studies on patient-derived dermal fibroblasts harboring RPL13 missense mutations demonstrated normal eL13 expression, with proper subcellular localization but reduced colocalization with eL28 (p < 0.001). Cellular functional defects in fibroblasts from mutation-positive subjects indicated a significant increase in the ratio of 60S subunits to 80S ribosomes (p = 0.007) and attenuated global translation (p = 0.017). In line with the human phenotype, our rpl13 mutant zebrafish model, generated by CRISPR-Cas9 editing, showed cartilage deformities at embryonic and juvenile stages. These findings extend the genetic spectrum of RPL13 mutations causing this novel human ribosomopathy with variable skeletal features. Our study underscores for the first time incomplete penetrance and broad phenotypic variability in SEMD-RPL13 type and confirms impaired ribosomal function. Furthermore, the newly generated rpl13 mutant zebrafish model corroborates the role of eL13 in skeletogenesis. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR)..

Biallelic variants p.Arg1133Cys and p.Arg1379Cys in COL2A1: Further delineation of phenotypic spectrum of recessive Type 2 collagenopathies.

The phenotypic spectrum of Type 2 collagenopathies ranges from lethal achondrogenesis Type 2 to milder osteoarthritis with mild chondrodysplasia. All of them are monoallelic except for the two recent reports showing that biallelic variants in COL2A1 can cause spondyloepiphyseal dysplasia congenita in two children. Here we report two additional families with homozygous variants, c.4135C>T (p.Arg1379Cys) and c.3190C>T (p.Arg1133Cys) in COL2A1 resulting in two distinct skeletal dysplasia phenotypes of intermediate severity. Though all six patients from four families exhibit a spondylo-epimetaphyseal dysplasia, they demonstrate a wide variation in severity of short stature and involvement of epiphyses, metaphyses, and vertebrae. We hypothesize that the variants are likely to be hypomorphic, given the underlying mechanisms of disease causation for known heterozygous variants in COL2A1. With this report, we provide further evidence to the existence of autosomal recessive Type 2 collagenopathy.

Novel loss-of-function variants of TRAPPC2 manifesting X-linked spondyloepiphyseal dysplasia tarda: report of two cases.

BACKGROUND: X-linked spondyloepiphyseal dysplasia tarda (SEDT-XL) is a skeletal disorder characterized by defective structures of vertebral bodies and/or of epiphyses of the long bones, resulting in moderately short stature and early joint degeneration. TRAPPC2 gene, which is important for collagen secretion, has been reported as causative for SEDT-XL. CASE PRESENTATION: Here, we report two variants of TRAPPC2 gene of SEDT-XL patients, a missense variant of start codon, c.1A > T, and a deletion variant, c.40delG. To understand molecular consequence of the variants, we establish an in vitro gene expression assay system and demonstrate that both mutated genes are transcribed, but are not properly translated, indicative of the pathogenic nature of those TRAPPC2 variants. CONCLUSIONS: In the current study, we provide additional experimental data showing that loss-of-function TRAPPC2 variants are probably causative for SEDT-XL phenotype. These findings further contribute to the understanding the clinical picture related to TRAPPC2 gene.

Hypomorphic Mutations in TONSL Cause SPONASTRIME Dysplasia.

SPONASTRIME dysplasia is a rare, recessive skeletal dysplasia characterized by short stature, facial dysmorphism, and aberrant radiographic findings of the spine and long bone metaphysis. No causative genetic alterations for SPONASTRIME dysplasia have yet been determined. Using whole-exome sequencing (WES), we identified bi-allelic TONSL mutations in 10 of 13 individuals with SPONASTRIME dysplasia. TONSL is a multi-domain scaffold protein that interacts with DNA replication and repair factors and which plays critical roles in resistance to replication stress and the maintenance of genome integrity. We show here that cellular defects in dermal fibroblasts from affected individuals are complemented by the expression of wild-type TONSL. In addition, in vitro cell-based assays and in silico analyses of TONSL structure support the pathogenicity of those TONSL variants. Intriguingly, a knock-in (KI) Tonsl mouse model leads to embryonic lethality, implying the physiological importance of TONSL. Overall, these findings indicate that genetic variants resulting in reduced function of TONSL cause SPONASTRIME dysplasia and highlight the importance of TONSL in embryonic development and postnatal growth.

Severe hypotonia and postnatal growth impairment in a girl with a missense mutation in COL1A1: Implication of expanded phenotypic spectrum of type I collagenopathy.

BACKGROUND: It is known that type I collagenopathy has a broad-spectrum phenotypic variability. Here, we report a case of a Korean girl with a heterozygous COL1A1 mutation who had an atypical presentation. CASE PRESENTATION: A 26-month-old girl presented with delayed motor development and failure to thrive. She had severe growth retardation. She exhibited right-sided plagiocephaly, blue sclerae, and facial dysmorphism, including a small pointed chin, frontal bossing, and a triangular face, but had microcephaly. Whole-exome sequencing revealed a novel de novo heterozygous sequence variant in COL1A1 (p.Gly1127Asp), which was validated by Sanger sequencing. Radiological finding showed generalized osteoporosis with progressive scoliosis of the spine without evidence of platyspondyly related to fractures and bowing of the long bones, and markedly delayed carpal bone age. Muscle pathology showed a marked size variation of myofibers and selective type 1 atrophy. CONCLUSIONS: This study expanded the clinical and genetic spectrum of type I collagenopathy with a COL1A1 variant. Therefore, we suggest that type I collagenopathy should be considered in the patients who have some features of osteogenesis imperfecta simultaneously with atypical features such as facial dysmorphism.

Autosomal dominant brachyolmia: transient metaphyseal striations.

We report transient proximal and distal femoral metaphyseal striations that have not previously been described in autosomal dominant brachyolmia. The pelvis/hip radiograph of a 13-year-old boy demonstrated bilaterally symmetrical proximal femoral metaphyseal vertical striations. Additional vertical striations were also observed at the distal femur and proximal tibia metaphysis. Radiography of the thoracolumbar spine demonstrated platyspondyly with irregular endplates and overfaced pedicles. TRPV4 mutations were confirmed in this patient. Similar proximal femoral metaphyseal vertical striations were noted in the patient's sibling. Those streaks disappeared on the follow-up radiographs, and we considered it a unique radiologic finding transiently observed in autosomal dominant brachyolmia.

Orthopedic Manifestations of Type I Camurati-Engelmann Disease.

BACKGROUND: Camurati-Engelmann disease (CED) is a rare genetic skeletal disorder characterized by limb pain, muscle emaciation and weakness, and cortical thickening of the diaphysis of long bones. It is caused by mutations in the transforming growth factor beta 1 (TGFB1) (type I) or other unknown gene(s) (type II). We present 8 consecutive patients with type I CED. METHODS: We retrospectively reviewed medical records and radiographs of type I CED patients with special reference to the mode of presentation, process of diagnostic work-up, and disease course. They were 4 sporadic patients, and two pairs of mother and son. RESULTS: We categorized the mode of presentation into three groups. Group I had 4 patients who mainly presented with motor disturbances in young age. They drew medical attention for waddling gait, awkward ambulation or running, difficulty in going upstairs, or a positive Gower's sign at age 4 to 6 years. Subsequent development of limb pain and radiographic abnormality led to the diagnosis of CED at age 6 to 29 years. Group II had 3 patients who mainly presented with limb pain at age 15, 20, and 54 years, respectively. Radiographic evaluation and molecular genetic test led to the diagnosis of CED. The remaining 1 patient (group III) was asymptomatic until age 9 years when bony lesions at the tibiae were found incidentally. For the last 10 years, he intermittently complained of leg pain in the morning or after sports activities, which did not interfere with daily life. All the patients in group I showed a body mass index in the underweight range (< 18.4 kg/m2). At the latest follow-up, 4 patients in groups I and II required medication for the limb pain. CONCLUSIONS: CED presents with a wide range of severity. Awareness of this rare disease entity may be the key to timely correct diagnosis. This disease entity should be considered in the differential diagnosis of limb pain or motor disturbance in children to avoid unnecessary diagnostic work-up.

Confirmation of CAGSSS syndrome as a distinct entity in a Danish patient with a novel homozygous mutation in IARS2.

Since the original description of the IARS2-related cataracts, growth hormone deficiency, sensory neuropathy, sensorineural hearing loss, skeletal dysplasia syndrome (CAGSSS; OMIM 616007) in an extended consanguineous family of French-Canadian descent, no further patients have been reported. IARS2 (OMIM 612801) encodes the mitochondrial isoleucine-tRNA synthetase which belongs to the class-I aminoacyl-tRNA synthetase family, and has been implicated in CAGSSS and a form of Leigh syndrome. Here, we report on a female Danish patient with a novel homozygous IARS2 mutation, p.Gly874Arg, who presented at birth with bilateral hip dislocation and short stature. At 3 months, additional dysmorphic features were noted and at 18 months her radiographic skeletal abnormalities were suggestive of an underlying spondyloepimetaphyseal dysplasia (SEMD). Retrospective analysis of the neonatal radiographs confirmed that the skeletal changes were present at birth. It was only with time that several of the other manifestations of the CAGSSS emerged, namely, cataracts, peripheral neuropathy, and hearing loss. Growth hormone deficiency has not (yet) manifested. We present her clinical features and particularly highlight her skeletal findings, which confirm the presence of a primary SEMD skeletal dysplasia in a growing list of mitochondrial-related disorders including CAGSSS, CODAS, EVEN-PLUS, and X-linked SEMD-MR syndromes.

Additional three patients with Smith-McCort dysplasia due to novel RAB33B mutations.

Smith-McCort dysplasia (SMC OMIM 615222) and Dyggve-Melchior-Clausen dysplasia (DMC OMIM 223800) are allelic skeletal dysplasias caused by homozygous or compound heterozygous mutations in DYM (OMIM 607461). Both disorders share the same skeletal phenotypes characterized by spondylo-epi-metaphyseal dysplasia with distinctive lacy ilia. The difference rests on the presence or absence of intellectual disability, that is, intellectual disability in DMC and normal cognition in SMC. However, genetic heterogeneity was suspected in SMC. Recently, RAB33B (OMIM 605950) has been identified as the second gene for SMC. Nevertheless, only two affected families have been reported so far. Here we present three SMC patients with four novel pathogenic variants in RAB33B, including homozygosity for c.211C>T (p.R71*), homozygosity for c.365T>C (p.F122S), and compound heterozygosity for c.48delCGGGGCAG (p.G17Vfs*58) and c.490C>T (p.Q164*). We also summarize the clinical, radiological, and mutation profile of RAB33B after literature mining. This report ascertains the pathogenic relationship between RAB33B and SMC. © 2017 Wiley Periodicals, Inc.

First Korean Case of Infantile Hypophosphatasia with Novel Mutation in ALPL and Literature Review.

Hypophosphatasia is a rare hereditary disorder characterized by defective bone and tooth mineralization and deficiency of tissue non-specific alkaline phosphatase activity. The prognosis for the infantile form is poor, with approximately 50% of patients dying within the first year of life from respiratory failure. We describe the clinical and biochemical findings as well as the molecular analysis of a Korean boy with infantile hypophosphatasia and present a literature review. A 1-month-old boy visited the clinic because of poor feeding, frequent vomiting, hypotonia, and failure to thrive from birth. Laboratory tests revealed high total calcium, low phosphorous, low alkaline phosphatase, low parathyroid hormone, and normal 25-hydroxyvitamin D. Intravenous hydration with normal saline was started, and dietary calcium intake was restricted. Skeletal X-rays showed a markedly increased distance of the anterior fontanelle, impaired mineralization, and rachitic changes in the metaphyses. By Sanger sequencing of the ALPL gene, we identified two heterozygous variants, including a missense (c.334G>A; p.Gly112Ser) and a nonsense (c.1039C>T; p.Gln347*) variant. The c.334G>A (p.Gly112Ser) variant had previously been reported in a patient with lethal type hypophosphatasia, while the nonsense c.1039C>T (p.Gln347*) variant was novel. In the current case, the accurate diagnosis and prompt intervention-including dietary calcium intake restriction, tracheostomy to prevent progression to respiratory failure, and fundoplication with gastrostomy to ensure the administration of adequate calories-seemed to play an important role for avoiding preventable morbidity and premature mortality.

Enhancing patterns of breast cancer on preoperative dynamic contrast-enhanced magnetic resonance imaging and resection margin in breast conserving therapy.

BACKGROUND: The association between enhancing patterns of preoperative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and resection margins after BCS has not been studied in detail before. OBJECTIVE: We investigated the association between surgical outcomes and enhancing patterns observed on DCE-MRI. METHODS: 269 enhancing patterns on DCE-MRI scans were selected, and subdivided into the following groups: (1) a single mass-like enhancement, (2) a single non-mass-like enhancement (NME), (3) mass-like enhancing breast cancer with other mass-like enhancing lesions, and (4) mass-like enhancing breast cancer with additional NMEs. Associations between enhancing patterns on DCE-MRI and re-excision rate, size of specimen, and ratio of tumor/specimen were evaluated retrospectively. RESULTS: The conversion rate from breast conserving therapy (BCT) to mastectomy as a result of MRI findings was 13.4%, re-excision rate during BCT was 8.2% and excision rate of another suspicious lesion was 7.4%. The single NME group had the highest re-excision rate after BCT (22.2%) (p = 0.02). The ratio of tumor/specimen (p = 0.61) and mean specimen size (p = 0.38) were not influenced by enhancement patterns. The false positive rate and positive predictive values of using DCE-MRI for defining the extension of breast cancer was 22.2% and 71.4%, respectively. CONCLUSION: Enhancement patterns on DCE- MRI, especially NME, could increase re-excision rates.

BGN Mutations in X-Linked Spondyloepimetaphyseal Dysplasia.

Spondyloepimetaphyseal dysplasias (SEMDs) comprise a heterogeneous group of autosomal-dominant and autosomal-recessive disorders. An apparent X-linked recessive (XLR) form of SEMD in a single Italian family was previously reported. We have been able to restudy this family together with a second family from Korea by segregating a severe SEMD in an X-linked pattern. Exome sequencing showed missense mutations in BGN c.439A>G (p.Lys147Glu) in the Korean family and c.776G>T (p.Gly259Val) in the Italian family; the c.439A>G (p.Lys147Glu) mutation was also identified in a further simplex SEMD case from India. Biglycan is an extracellular matrix proteoglycan that can bind transforming growth factor beta (TGF-ß) and thus regulate its free concentration. In 3-dimensional simulation, both altered residues localized to the concave arc of leucine-rich repeat domains of biglycan that interact with TGF-ß. The observation of recurrent BGN mutations in XLR SEMD individuals from different ethnic backgrounds allows us to define "XLR SEMD, BGN type" as a nosologic entity.

Identification of the Mutations in the Prostaglandin Transporter Gene, SLCO2A1 and Clinical Characterization in Korean Patients with Pachydermoperiostosis.

Pachydermoperiostosis (PDP), or primary hypertrophic osteoarthropathy, is a rare genetic disease affecting both skin and bones. Both autosomal dominant with incomplete penetrance and recessive inheritance of PDP have been previously confirmed. Recently, hydroxyprostaglandin dehydrogenase (HPGD) and solute carrier organic anion transporter family member 2A1 (SLCO2A1) were reported as pathogenic genes responsible for PDP. Both genes are involved in prostaglandin E2 (PGE2) degradation. We aimed to identify responsible genes for PDP and the clinical features in Korean patients with PDP. Six affected individuals and their available healthy family members from three unrelated Korean families with PDP were studied. All of the patients displayed complete phenotypes of PDP with finger clubbing, pachydermia, and periostosis. Mutation analysis revealed a novel heterozygous mutation in the SLCO2A1 gene at nucleotide 302 causing a substitution of the amino acid isoleucine to serine at codon 101 (p.IIe101Ser) in affected individuals. We also identified known SLCO2A1 mutations, one homozygous for c.940+1G>A, and another compound heterozygous for c.940+1G>A and c.1807C>T (p.Arg603*) from two PDP families. Genetic analyses of the PDP patients showed no abnormality in the HPGD gene. Our study further supports the role of mutations in the SLCO2A1 gene in the pathogenesis of PDP and could provide additional clues to the genotype-phenotype relations of PDP.

Axial Spondylometaphyseal Dysplasia Is Caused by C21orf2 Mutations.

Axial spondylometaphyseal dysplasia (axial SMD) is an autosomal recessive disease characterized by dysplasia of axial skeleton and retinal dystrophy. We conducted whole exome sequencing and identified C21orf2 (chromosome 21 open reading frame 2) as a disease gene for axial SMD. C21orf2 mutations have been recently found to cause isolated retinal degeneration and Jeune syndrome. We found a total of five biallelic C21orf2 mutations in six families out of nine: three missense and two splicing mutations in patients with various ethnic backgrounds. The pathogenic effects of the splicing (splice-site and branch-point) mutations were confirmed on RNA level, which showed complex patterns of abnormal splicing. C21orf2 mutations presented with a wide range of skeletal phenotypes, including cupped and flared anterior ends of ribs, lacy ilia and metaphyseal dysplasia of proximal femora. Analysis of patients without C21orf2 mutation indicated genetic heterogeneity of axial SMD. Functional data in chondrocyte suggest C21orf2 is implicated in cartilage differentiation. C21orf2 protein was localized to the connecting cilium of the cone and rod photoreceptors, confirming its significance in retinal function. Our study indicates that axial SMD is a member of a unique group of ciliopathy affecting skeleton and retina.

SOFT syndrome caused by compound heterozygous mutations of POC1A and its skeletal manifestation.

SOFT syndrome (MIM614813) is an extremely rare primordial dwarfism characterized by short stature, onychodysplasia, facial dysmorphism and hypotrichosis, which is caused by biallelic mutations in the POC1A gene. Only 19 patients with mutation-confirmed SOFT syndrome have been reported to date, all of whom carried homozygous variants that were strongly associated with consanguineous marriages. We report an 8.5-year-old boy with SOFT syndrome showing primordial dwarfism, no effect of growth-hormone therapy and skeletal dysplasia. This is the first report of compound heterozygous variants in POC1A, one previously reported and the other novel. A characteristic skeletal manifestation is reported.