Phenotypic and Molecular Spectrum of a Turkish Cohort with Hereditary Multiple Osteochondromas.

OBJECTIVE: Hereditary multiple osteochondromas is an autosomal dominant disorder caused by heterozygous pathogenic variants in EXT1 or EXT2. We aimed to evaluate the clinical and molecular findings of a Turkish cohort with hereditary multiple osteochondroma. MATERIALS AND METHODS: Thirty-two patients aged 1.3-49.6 years from 22 families were enrolled. Genetic analyses were made by EXT1 and/or EXT2 sequencing and chromosomal microarray analyses. RESULTS: We found 17 intragenic pathogenic variants in EXT1 (13/17) and EXT2 (4/17), 12 of which are novel. Four probands had EXT1 deletions, including 2 patients with partial EXT1 microdeletions involving exons 2-11 and 5-11, and 2 patients with whole-gene deletions. In 21 variants, the frequency of truncating and missense variants was 76.1% and 23.8%, respectively. Two families had no detectable variants in EXT1 and EXT2. All patients had multiple osteochondromas at the long bones, mainly at the tibia, forearm, femur, and humerus. Bowing deformity of the forearms (9/32) and the lower extremities (2/32), and scoliosis (6/32) were observed. The clinical severity was not different between patients with EXT1 or EXT2 variants. One patient with an EXT2 variant and another with an EXT1 microdeletion had the most severe phenotype with class III disease. Four patients with no EXT1 or EXT2 variants had milder phenotypes. Intrafamilial variability in disease severity was not observed. CONCLUSION: We report a hereditary multiple osteochondroma cohort with clinical and molecular data including 12 novel intragenic variants in EXT1 or EXT2, and 4 microdeletions involving EXT1. Taken together, our data expand the existing knowledge of the phenotype-genotype spectrum in hereditary multiple osteochondroma.

Expanding the clinical and molecular features of trichorhino- phalangeal syndrome with a novel variant.

BACKGROUND: Tricho-rhino-phalangeal syndrome (TRPS) is a rare, autosomal dominant disorder characterized by typical craniofacial features, ectodermal and skeletal findings. TRPS type 1 (TRPS1) is caused by pathogenic variations in the TRPS1 gene, which relates to the vast majority of cases. TRPS type 2 (TRPS2) is a contiguous gene deletion syndrome involving loss of functional copies of the TRPS1, RAD21, and EXT1. Herein, we reported the clinical and genetic spectrum of seven TRPS patients with a novel variant. We also reviewed the musculoskeletal and radiological findings in the literature. METHODS: Seven Turkish patients (three female, four male) from five unrelated families aged between 7 to 48 years were evaluated. The clinical diagnosis was confirmed by either molecular karyotyping or TRPS1 sequencing analysis via next-generation sequencing. RESULTS: Both TRPS1 and TRPS2 patients had some common distinctive facial features and skeletal findings. All patients had a bulbous nose with hypoplastic alae nasi, brachydactyly, short metacarpals and phalanges in variable stages. Low bone mineral density (BMD) was identified in two TRPS2 family members presenting with bone fracture, and growth hormone deficiency was detected in two patients. Skeletal X-ray imaging revealed cone-shaped epiphysis of the phalanges in all, and multiple exostoses were present in three patients. Cerebral hamartoma, menometrorrhagia and long bone cysts were among the new/rare conditions. Three pathogenic variants in TRPS1 were identified in four patients from three families, including a frameshift (c.2445dup, p.Ser816GlufsTer28), one missense (c.2762G > A), and a novel splice site variant (c.2700+3A > G). We also reported a familial inheritance in TRPS2 which is known to be very rare. CONCLUSIONS: Our study contributes to the clinical and genetic spectrum of patients with TRPS while also providing a review by comparing with previous cohort studies.

Skeletal and molecular findings in 51 Cleidocranial dysplasia patients from Turkey.

Loss or decrease of function in runt-related transcription factor 2 encoded by RUNX2 is known to cause a rare autosomal-dominant skeletal disorder, cleidocranial dysplasia (CCD). Clinical spectrum and genetic findings in 51 CCD patients from 30 unrelated families are herein presented. In a majority of the patients, facial abnormalities, such as delayed fontanel closure (89%), parietal and frontal bossing (80%), metopic groove (77%), midface hypoplasia (94%), and abnormal mobility of shoulders (90%), were recorded following clinical examination. In approximately one-half of the subjects, wormian bone (51%), short stature (43%), bell-shaped thorax (42%), wide pubic symphysis (50%), hypoplastic iliac wing (59%), and chef's hat sign (44%) presented in available radiological examinations. Scoliosis was identified in 28% of the patients. Investigation of RUNX2 revealed small sequence alterations in 90% and gross deletions in 10% of the patients; collectively, 23 variants including 11 novel changes (c.29_30insT, c.203delAinsCG, c.423 + 2delT, c.443_454delTACCAGATGGGAinsG, c.505C > T, c.594_595delCTinsG, c.636_637insC, c.685 + 5G > A, c.1088G > T, c.1281delC, Exon 6-9 deletion) presented high allelic heterogeneity. Novel c.29_30insT is unique in affecting the P1-driven long isoform of RUNX2, which is expected to disrupt the N-terminal region of RUNX2; this was shown in two unrelated phenotypically discordant patients. The clinical findings highlighted mild intra-familial genotype-phenotype correlation in our CCD cohort.

Further defining the clinical and molecular spectrum of acromesomelic dysplasia type maroteaux: a Turkish tertiary center experience.

Acromesomelic dysplasia type Maroteaux (AMDM, OMIM #602875) is an autosomal recessive disorder characterized by severe short stature, shortened middle and distal segments of the limbs, redundant skin of fingers, radial head subluxation or dislocation, large great toes and cranium, and normal intelligence. Only the skeletal system appears to be consistently affected. AMDM is caused by biallelic loss-of-function variants in the natriuretic peptide receptor B (NPRB or NPR2, OMIM #108961) which is involved in endochondral ossification and longitudinal growth of limbs and vertebrae. In this study, we investigated 26 AMDM patients from 22 unrelated families and revealed their genetic etiology in 20 families, via Sanger sequencing or exome sequencing. A total of 22 distinct variants in NPR2 (14 missense, 5 nonsense, 2 intronic, and 1 one-amino acid deletion) were detected, among which 15 were novel. They were in homozygous states in 19 patients and in compound heterozygous states in four patients. Parents with heterozygous NPR2 variants were significantly shorter than the control. Extra-skeletal abnormalities, including global developmental delay/intellectual disability, nephrolithiasis, renal cyst, and oligodontia were noted in the patient cohort. The high parental consanguinity rate might have contributed to these findings, probably associated with other gene variants. This study represents the largest cohort of AMDM from Turkey and regional countries and further expands the molecular and clinical spectrum of AMDM.

Biallelic variants in KYNU cause a multisystemic syndrome with hand hyperphalangism.

Catel-Manzke syndrome is characterized by the combination of Pierre Robin sequence and radial deviation, shortening as well as clinodactyly of the index fingers, due to an accessory ossification center. Mutations in TGDS have been identified as one cause of Catel-Manzke syndrome, but cannot be found as causative in every patient with the clinical diagnosis. We performed a chromosome microarray and/or exome sequencing in three patients with hand hyperphalangism, heart defect, short stature, and mild to severe developmental delay, all of whom were initially given a clinical diagnosis of Catel-Manzke syndrome. In one patient, we detected a large deletion of exons 1-8 and the missense variant c.1282C > T (p.Arg428Trp) in KYNU (NM_003937.2), whereas homozygous missense variants in KYNU were found in the other two patients (c.989G > A (p.Arg330Gln) and c.326G > C (p.Trp109Ser)). Plasma and urine metabolomic analysis of two patients indicated a block along the tryptophan catabolic pathway and urine organic acid analysis showed excretion of xanthurenic acid. Biallelic loss-of-function mutations in KYNU were recently described as a cause of NAD deficiency with vertebral, cardiac, renal and limb defects; however, no hand hyperphalangism was described in those patients, and Catel-Manzke syndrome was not discussed as a differential diagnosis. In conclusion, we present unrelated patients identified with biallelic variants in KYNU leading to kynureninase deficiency and xanthurenic aciduria as a very likely cause of their hyperphalangism, heart defect, short stature, and developmental delay. We suggest performance of urine organic acid analysis in patients with suspected Catel-Manzke syndrome, particularly in those with cardiac or vertebral defects or without mutations in TGDS.

Clinical and genetic findings of two cases with Apert syndrome.

Background: Craniosynostosis is described as the premature fusion of cranial sutures that belongs to a group of alterations which produce an abnormal phenotype. Case report: Two unrelated female patients with clinical findings of Apert syndrome-characterized by acrocephaly, prominent frontal region, flat occiput, ocular proptosis, hypertelorism, down-slanted palpebral fissures, midfacial hypoplasia, high-arched or cleft palate, short neck, cardiac anomalies and symmetrical syndactyly of the hands and feet-are present. In both patients, a heterozygous missense mutation (c.755C>G, p.Ser252Trp) in the FGFR2 gene was identified. Conclusions: Two cases of Apert syndrome are described. It is important to recognize this uncommon entity through clinical findings, highlight interdisciplinary medical evaluation, and provide timely genetic counseling for the family.

Introducción: Las craneosinostosis se describen como la fusión prematura de las suturas craneales y resultan un grupo de alteraciones que producen un fenotipo anormal. Caso clínico: En este informe de casos se presentan dos pacientes de sexo femenino no emparentadas con hallazgos clínicos del síndrome de Apert, caracterizado por acrocefalia, región frontal prominente, occipucio plano, proptosis ocular, hipertelorismo, fisuras palpebrales hacia abajo, hipoplasia mediofacial, paladar alto o hendido, cuello corto, cardiopatía congénita y sindactilia simétrica en manos y pies. En ambas pacientes se identificó una mutación cambio de sentido en heterocigosis (c.755C>G, p.Ser252Trp) en el gen FGFR2. Conclusiones: Se presentan dos casos de síndrome de Apert. Es importante reconocer a través de los hallazgos clínicos esta entidad infrecuente, resaltar la evaluación médica interdisciplinaria y proporcionar un oportuno asesoramiento genético a la familia.

A subset of patients with acquired partial lipodystrophy developing severe metabolic abnormalities.

Purpose/Aim of the study: Acquired partial lipodystrophy (APL) is a rare disease characterized by selective loss of adipose tissue. In this study, we aimed to present a subset of patients with APL, who developed severe metabolic abnormalities, from our national lipodystrophy registry. MATERIALS AND METHODS: Severe metabolic abnormalities were defined as: poorly controlled diabetes (HbA1c above 7% despite treatment with insulin more than 1 unit/kg/day combined with oral antidiabetics), severe hypertriglyceridemia (triglycerides above 500 mg/dL despite treatment with lipid-lowering drugs), episodes of acute pancreatitis, or severe hepatic involvement (biopsy-proven non-alcoholic steatohepatitis (NASH)). RESULTS: Among 140 patients with all forms of lipodystrophy (28 with APL), we identified 6 APL patients with severe metabolic abnormalities. The geometric mean for age was 37 years (range: 27-50 years; 4 females and 2 males). Five patients had poorly controlled diabetes despite treatment with high-dose insulin combined with oral antidiabetics. Severe hypertriglyceridemia developed in five patients, of those three experienced episodes of acute pancreatitis. Although all six patients had hepatic steatosis at various levels on imaging studies, NASH was proven in two patients on liver biopsy. Our data suggested that APL patients with severe metabolic abnormalities had a more advanced fat loss and longer disease duration. CONCLUSIONS: We suggest that these patients represent a potential subgroup of APL who may benefit from metreleptin or investigational therapies as standard treatment strategies fail to achieve a good metabolic control.

SLC10A7 mutations cause a skeletal dysplasia with amelogenesis imperfecta mediated by GAG biosynthesis defects.

Skeletal dysplasia with multiple dislocations are severe disorders characterized by dislocations of large joints and short stature. The majority of them have been linked to pathogenic variants in genes encoding glycosyltransferases, sulfotransferases or epimerases required for glycosaminoglycan synthesis. Using exome sequencing, we identify homozygous mutations in SLC10A7 in six individuals with skeletal dysplasia with multiple dislocations and amelogenesis imperfecta. SLC10A7 encodes a 10-transmembrane-domain transporter located at the plasma membrane. Functional studies in vitro demonstrate that SLC10A7 mutations reduce SLC10A7 protein expression. We generate a Slc10a7-/- mouse model, which displays shortened long bones, growth plate disorganization and tooth enamel anomalies, recapitulating the human phenotype. Furthermore, we identify decreased heparan sulfate levels in Slc10a7-/- mouse cartilage and patient fibroblasts. Finally, we find an abnormal N-glycoprotein electrophoretic profile in patient blood samples. Together, our findings support the involvement of SLC10A7 in glycosaminoglycan synthesis and specifically in skeletal development.

Early postoperative follow-up after craniosynostosis surgery

Background/aim: Declined morbidity rates after craniosynostosis surgery indicate bypassing the pediatric intensive care unit (PICU) course to minimize treatment costs and bed usage. The aim of this study is to examine the incident rates of PICU admission and assess its necessity. Materials and methods: A retrospective analysis of 41 patients (operated on by open surgical techniques) between July 2011 and December 2015 was carried out. Intraoperative/postoperative vital signs, hemodynamic and metabolic parameters, estimated blood loss (EBVloss), blood transfusions, length of PICU, and hospitalizations were recorded. Results: Major and minor events reached 51.2% and 82.9%, respectively. EBVloss within 24 h was calculated as 39.58 ± 8.19 (median: 38.44, 25.68-66.34) with 75.6% blood transfusion rate. Hypotension and hypothermia were associated with prolonged surgery (P = 0.001 and P = 0.007, respectively), but were not related to age (P = 0.054, P = 0.162) or procedure types (P = 0.558, P = 0.663). Prolonged surgery and younger age had an impact on the complications. One patient died of persistent hemorrhage at 96 h. Conclusion: Monitoring cardiovascular and metabolic dynamics at PICU during the first 24 h after surgery is crucial. Additional studies are needed to define the threshold values of several metabolic and hemodynamic markers in risk assessment after cranial vault surgery.

Overlapping SETBP1 gain-of-function mutations in Schinzel-Giedion syndrome and hematologic malignancies.

Schinzel-Giedion syndrome (SGS) is a rare developmental disorder characterized by multiple malformations, severe neurological alterations and increased risk of malignancy. SGS is caused by de novo germline mutations clustering to a 12bp hotspot in exon 4 of SETBP1. Mutations in this hotspot disrupt a degron, a signal for the regulation of protein degradation, and lead to the accumulation of SETBP1 protein. Overlapping SETBP1 hotspot mutations have been observed recurrently as somatic events in leukemia. We collected clinical information of 47 SGS patients (including 26 novel cases) with germline SETBP1 mutations and of four individuals with a milder phenotype caused by de novo germline mutations adjacent to the SETBP1 hotspot. Different mutations within and around the SETBP1 hotspot have varying effects on SETBP1 stability and protein levels in vitro and in in silico modeling. Substitutions in SETBP1 residue I871 result in a weak increase in protein levels and mutations affecting this residue are significantly more frequent in SGS than in leukemia. On the other hand, substitutions in residue D868 lead to the largest increase in protein levels. Individuals with germline mutations affecting D868 have enhanced cell proliferation in vitro and higher incidence of cancer compared to patients with other germline SETBP1 mutations. Our findings substantiate that, despite their overlap, somatic SETBP1 mutations driving malignancy are more disruptive to the degron than germline SETBP1 mutations causing SGS. Additionally, this suggests that the functional threshold for the development of cancer driven by the disruption of the SETBP1 degron is higher than for the alteration in prenatal development in SGS. Drawing on previous studies of somatic SETBP1 mutations in leukemia, our results reveal a genotype-phenotype correlation in germline SETBP1 mutations spanning a molecular, cellular and clinical phenotype.

Natural History of Congenital Generalized Lipodystrophy: A Nationwide Study From Turkey.

CONTEXT: Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by near-total lack of body fat. OBJECTIVE: We aimed to study natural history and disease burden of various subtypes of CGL. DESIGN: We attempted to ascertain nearly all patients with CGL in Turkey. SETTING: This was a nationwide study. PATIENTS OR OTHER PARTICIPANTS: Participants included 33 patients (22 families) with CGL and 30 healthy controls. MAIN OUTCOME MEASURE(S): We wanted to ascertain genotypes by sequencing of the known genes. Whole-body magnetic resonance imaging was used to investigate the extent of fat loss. Metabolic abnormalities and end-organ complications were measured on prospective follow-up. RESULTS: Analysis of the AGPAT2 gene revealed four previously reported and four novel mutations (CGL1; c.144C>A, c.667_705delinsCTGCG, c.268delC, and c.316+1G>T). Analysis of the BSCL2 gene revealed four different homozygous and one compound heterozygous possible disease-causing mutations (CGL2), including four novel mutations (c.280C>T, c.631delG, c.62A>T, and c.465-468delGACT). Two homozygous PTRF mutations (c.481-482insGTGA and c.259C>T) were identified (CGL4). Patients with CGL1 had preservation of adipose tissue in the palms, soles, scalp, and orbital region, and had relatively lower serum adiponectin levels as compared to CGL2 patients. CGL4 patients had myopathy and other distinct clinical features. All patients developed various metabolic abnormalities associated with insulin resistance. Hepatic involvement was more severe in CGL2. End-organ complications were observed at young ages. Two patients died at age 62 years from cardiovascular events. CONCLUSIONS: CGL patients from Turkey had both previously reported and novel mutations of the AGPAT2, BSCL2, and PTRF genes. Our study highlights the early onset of severe metabolic abnormalities and increased risk of end-organ complications in patients with CGL.

Perinatal Diagnostic Approach to Fetal Skeletal Dysplasias: Six Years Experience of a Tertiary Center.

Skeletal dysplasias (SDs) constitute a group of heterogeneous disorders affecting growth morphology of the chondro-osseous tissues. Prenatal diagnosis of SD is a considerable clinical challenge due to phenotypic variability. We performed a retrospective analysis of the fetal autopsies series conducted between January 2006 and December 2012 at our center. SD was detected in 54 (10%) out of 542 fetal autopsy cases which included; 11.1% thanatophoric dysplasia (n = 6), 7.4% achondroplasia (n = 4), 3.7% osteogenesis imperfect (n = 2), 1.9% Jarcho-Levin Syndrome (n = 1), 1.9% arthrogryposis (n = 1), 1.9% Dyggve-Melchior-Clausen syndrome (n = 1), 72.1% of dysostosis cases (n = 39). All SD cases were diagnosed by ultrasonography. In 20 of the cases, amniocentesis was performed, 4 cases underwent molecular genetic analyses. Antenatal identification of dysplasia is important in the management of pregnancy and in genetic counseling. Our data analysis showed that SD is usually detected clinically after the 20th gestational week. Genetic analyses for SD may provide early diagnosis and management.

Celiac disease in patients with Williams-Beuren syndrome.

Celiac disease is an autoimmune, gastrointestinal disorder characterized by intolerance to the dietary grain protein gluten. An increased prevalence of celiac disease has been reported in Down syndrome and Turner syndrome, but there has been only few previous reports with respect to the association of celiac disease in Williams-Beuren syndrome. The aim of this study was to evaluate the frequency of celiac disease in our 24 Williams-Beuren syndrome patients. Gastrointestinal problems and celiac disease symptoms of patients were noted. All patients were analyzed by the titer of tissue transglutaminases IgA and IgG. HLA genotyping and intestinal biopsy was performed to the patients with positive serology. We also performed gluten free diet in the presence of compatible symptoms, serology, HLA genotyping and intestinal biopsy. In our study, two patients had positive tTG antibodies, but only one had positive biopsy finding for celiac disease. The frequency of celiac disease in patients with Williams-Beuren syndrome was estimated as 1/24 (4.1%). Though the number of participants in this study was limited, the results show that the frequency of celiac disease is higher in Williams-Beuren syndrome compared to the general population. We suggest that a high suspicion and testing for celiac disease should be recommended at certain intervals in all cases with Williams-Beuren syndrome to detect the cause of growth retardation and gastrointestinal problems.

Clinicogenetic study of Turkish patients with syndromic craniosynostosis and literature review.

BACKGROUND: Fibroblast growth factor receptor 2 mutations have been associated with the craniosynostotic conditions of Apert, Crouzon, Pfeiffer, Saethre-Chotzen, Jackson-Weiss, Beare-Stevenson cutis gyrata, and Antley-Bixler syndromes in various ethnic groups. METHODS: Thirty-three unrelated Turkish patients (12 with Apert syndrome, 14 with Crouzon syndrome, six with Pfeiffer syndrome, and one with Saethre-Chotzen syndrome) and 67 nonsyndromic craniosynostosis patients were screened for mutations in exons IIIa and IIIc of the FGFR2 gene by denaturing high-performance liquid chromatography and confirmed by direct sequencing. RESULTS: We detected several pathogenic mutations in 11/33 (33%) patients with Apert syndrome (four with p.Pro253Arg; seven with p.Ser252Trp) and 8/33 (24%) patients with Crouzon syndrome (three with p.Trp290Arg, one with p.Cys342Tyr, p.Cys278Phe, p.Gln289Pro, and a novel p.Tyr340Asn mutation) and five (15%) with Pfeiffer syndrome (p.Cys342Arg, p.Pro253Arg, p.Trp290Arg, and p.Ser351Cys). No FGFR2 gene mutation was detected in any of the patients with Saethre-Chotzen syndrome and nonsyndromic craniosynostosis. CONCLUSIONS: Our results indicate that the majority of Turkish patients with syndromic craniosynostosis have detectable genetic changes with an overall frequency of 72.7%. Because this is the first molecular genetic report from a Turkish cohort, the identified spectrum profile of FGFR2 mutations of the syndromic craniosynostotic patients would be very helpful for understanding the genotype-phenotype relationship and has a great value for diagnosis, prognosis, and genetic counseling.

The association of Klinefelter syndrome and multiple pterygium syndrome: an unusual presentation.

Multiple pterygium syndrome is characterized by a number of phenotypic features, small stature, webbing of the neck, elbows, and/or knees, and joint contractures. In this report, we present an 11-year-old boy who had the classical findings of multiple pterygium syndrome, and his chromosomal analysis revealed a 47,XXY karyotype. Interestingly, he did not show any of the main clinical signs of Klinefelter syndrome. This patient appears to be the first reported case in the literature in which a non-mosaic 47,XXY karyotype has been found in a patient with multiple pterygium syndrome. The aim of the present report is to describe a non-classic Klinefelter syndrome associated with multiple pterygium syndrome and to emphasize the importance of karyotype analysis in patients with multiple pterygium syndrome.

Severe neurologic manifestations from cervical spine instability in spondylo-megaepiphyseal-metaphyseal dysplasia.

Spondylo-megaepiphyseal-metaphyseal dysplasia (SMMD; OMIM 613330) is a dysostosis/dysplasia caused by recessive mutations in the homeobox-containing gene, NKX3-2 (formerly known as BAPX1). Because of the rarity of the condition, its diagnostic features and natural course are not well known. We describe clinical and radiographic findings in six patients (five of which with homozygous mutations in the NKX3-2 gene) and highlight the unusual and severe changes in the cervical spine and the neurologic complications. In individuals with SMMD, the trunk and the neck are short, while the limbs, fingers and toes are disproportionately long. Radiographs show a severe ossification delay of the vertebral bodies with sagittal and coronal clefts, missing ossification of the pubic bones, large round "balloon-like" epiphyses of the long bones, and presence of multiple pseudoepiphyses at all metacarpals and phalanges. Reduced or absent ossification of the cervical vertebrae leads to cervical instability with anterior or posterior kinking of the cervical spine (swan neck-like deformity, kyknodysostosis). As a result of the cervical spine instability or deformation, five of six patients in our series suffered cervical cord injury that manifested clinically as limb spasticity. Although the number of individuals observed is small, the high incidence of cervical spine deformation in SMMD is unique among skeletal dysplasias. Early diagnosis of SMMD by recognition of the radiographic pattern might prevent of the neurologic complications via prophylactic cervical spine stabilization.

Wolcott-Rallison syndrome due to a novel mutation (R491X) in EIF2AK3 gene.

Wolcott-Rallison syndrome (WRS) is a rare autosomal recessive disorder characterized by early-onset diabetes, spondyloepiphyseal dysplasia, tendency to skeletal fractures secondary to osteopenia, and growth retardation. Mutations in the eukaryotic translation initiation factor 2α kinase (EIF2AK3) gene are responsible for this disorder. Here, we describe a boy with neonatal diabetes, diagnosed at 2 months of age, who developed severe growth retardation and a skeletal fracture during the follow-up period. The patient's skeletal X-ray revealed findings of skeletal dysplasia. A clinical diagnosis of WRS was confirmed by the identification of a novel homozygous nonsense mutation (R491X) in exon 9 of the EIF2AK3 gene. The aim of this report is to raise the awareness for Wolcott-Rallison syndrome in cases presenting with isolated neonatal diabetes. This patient demonstrates that the other findings of this syndrome might be obscured by a diagnosis of isolated neonatal diabetes.

Molecular and clinical heterogeneity in CLCN7-dependent osteopetrosis: report of 20 novel mutations.

The "Osteopetroses" are genetic diseases whose clinical picture is caused by a defect in bone resorption by osteoclasts. Three main forms can be distinguished on the basis of severity, age of onset and means of inheritance: the dominant benign, the intermediate and the recessive severe form. While several genes have been involved in the pathogenesis of the different types of osteopetroses, the CLCN7 gene has drawn the attention of many researchers, as mutations within this gene are associated with very different phenotypes. We report here the characterization of 25 unpublished patients which has resulted in the identification of 20 novel mutations, including 11 missense mutations, 6 causing premature termination, 1 small deletion and 2 putative splice site defects. Careful analysis of clinical and molecular data led us to several conclusions. First, intermediate osteopetrosis is not homogeneous, since it can comprise both severe dominant forms with an early onset and recessive ones without central nervous system involvement. Second, the appropriateness of haematopoietic stem cell transplantation in CLCN7-dependent ARO patients has to be carefully evaluated and exhaustive CNS examination is strongly suggested, as transplantation can almost completely cure the disease in situations where no primary neurological symptoms are present. Finally, the analysis of this largest cohort of CLCN7-dependent ARO patients together with some ADO II families allowed us to draw preliminary genotype-phenotype correlations suggesting that haploinsufficiency is not the mechanism causing ADO II. The availability of biochemical assays to characterize ClC-7 function will help to confirm this hypothesis.

Homozygous inactivating mutations in the NKX3-2 gene result in spondylo-megaepiphyseal-metaphyseal dysplasia.

Spondylo-megaepiphyseal-metaphyseal dysplasia (SMMD) is a rare skeletal dysplasia with only a few cases reported in the literature. Affected individuals have a disproportionate short stature with a short and stiff neck and trunk. The limbs appear relatively long and may show flexion contractures of the distal joints. The most remarkable radiographic features are the delayed and impaired ossification of the vertebral bodies as well as the presence of large epiphyseal ossification centers and wide growth plates in the long tubular bones. Numerous pseudoepiphyses of the short tubular bones in hands and feet are another remarkable feature of the disorder. Genome wide homozygosity mapping followed by a candidate gene approach resulted in the elucidation of the genetic cause in three new consanguineous families with SMMD. Each proband was homozygous for a different inactivating mutation in NKX3-2, a homeobox-containing gene located on chromosome 4p15.33. Striking similarities were found when comparing the vertebral ossification defects in SMMD patients with those observed in the Nkx3-2 null mice. Distinguishing features were the asplenia found in the mutant mice and the radiographic abnormalities in the limbs only observed in SMMD patients. The absence of the latter anomalies in the murine model may be due to the perinatal death of the affected animals. This study illustrates that NKX3-2 plays an important role in endochondral ossification of both the axial and appendicular skeleton in humans. In addition, it defines SMMD as yet another skeletal dysplasia with autosomal-recessive inheritance and a distinct phenotype.