Association between periacetabular osteotomy and hip dysplasia among relatives: a cross-sectional study.

INTRODUCTION: Previous studies indicate a familial predisposition for developmental dysplasia of the hip (DDH), especially among first-degree relatives. This study investigated the association between unilateral or bilateral periacetabular osteotomy (PAO), family history of DDH and the degree of relationship with relatives with DDH. MATERIAL AND METHODS: This cross-sectional study consisted of 815 consecutive patients undergoing PAO from 1998 to 2016. Information regarding unilateral or bilateral PAO, gender and age at the time of surgery was obtained from the clinical PAO database at Aarhus University Hospital, Denmark. A questionnaire was used to collect information about the family history of DDH. The association was assessed by logistic regression analysis, and divided into 615 unilateral and 200 bilateral PAO patients. RESULTS: PAO patients with a first-degree relative with DDH had a 72% (odds ratio [OR] = 1.72, 95% confidence interval [CI] 1.17; 2.50) higher occurrence of bilateral PAO than patients without family relatives with DDH. This association was statistically significant (p = 0.005), even when adjusting for gender and age at the time of surgery. A similar association was not demonstrated among any other degrees of relationship. CONCLUSION: Danish patients with DDH and a first-degree relative with DDH have an increased risk of being surgically treated with bilateral PAO compared to patients without a family history of DDH. Patients undergoing bilateral PAO may therefore have a strong genetic predisposition for DDH. This study reveals a potential group of patients with DDH where genetic analysis may identify relatives with a higher risk of the disease.

Chromosomal Aberrations in Monozygotic and Dizygotic Twins Versus Singletons in Denmark During 1968-2009.

BACKGROUND: Hall (Embryologic development and monozygotic twinning. Acta Geneticae Medicae et Gemellologiae, Vol. 45, 1996, pp. 53-57) hypothesized that chromosomal aberrations can lead to monozygotic (MZ) twinning. However, twinning and chromosomal aberrations increase prenatal mortality and could reduce the prevalence of chromosomal aberrations in live-born twins. We compared prevalence proportion ratios (PPR) of chromosomal aberrations and trisomy 21 (T21) in live-born twins versus singletons born in Denmark during 1968-2009. METHODS: We linked the Danish Twin Registry and a 5% random sample of all singletons to the Danish Cytogenetic Central Register and calculated PPR adjusted for maternal age for MZ, dizygotic (DZ), and all twins versus singletons. Zygosity was based on questionnaires or genetic markers. RESULTS: No overall difference in risk of chromosomal aberrations or T21 in twins versus singletons was found. PPR in MZ and DZ twins was 0.87 (95% CI [0.60, 1.27]) and 1.05 (95% CI [0.88, 1.27]), respectively. For T21 there was a tendency to a lower prevalence in MZ twins compared to singletons (PPR: 0.29, 95% CI [0.07, 1.14]), whereas PPR was significantly increased in DZ twins (1.62, 95% CI [1.20, 2.19]). The observed proportion of MZ twin pairs among twin pairs with aberrations (0.22, 95% CI [0.16, 0.28]) was significantly lower than the proportion expected from the Weinberg method (0.32, 95% CI [CI, 0.26, 0.39]). CONCLUSION: Based on databases providing complete national coverage on twins with chromosomal aberrations, we found no overall difference in risk of chromosomal aberrations or T21 in twins versus singletons. Around conception twins may have an increased risk of chromosomal aberrations, but loss of especially MZ embryos could lead to similar risk among live-born twins and singletons.

The association between gender and familial prevalence of hip dysplasia in Danish patients.

BACKGROUND: The development of hip dysplasia is associated with several risk factors. 1 of these risk factors is gender, since 80% of patients with symptomatic hip dysplasia are females. Another risk factor for hip dysplasia is familial predisposition of hip dysplasia. Several studies indicate that the risk of hip dysplasia is increased with familial prevalence of hip dysplasia. However, little is known about the association between the familial prevalence and gender and the development of hip dysplasia. PURPOSE: The aim of the study was to estimate the prevalence of hip dysplasia among relatives to Danish patients with hip dysplasia operated with periacetabular osteotomy (PAO), and the degree of relationship of affected family members. Furthermore, to assess the association between gender and family predisposition in the same group of patients. METHOD: The study is a cross-sectional study, with a descriptive and an analytical part. The study population consists of 676 patients drawn from a clinical database of patients operated with PAO at Aarhus University hospital from 1998 to 2014. Information about gender, operated hip side and age was collected from the clinical PAO database, while information about familial prevalence was collected through questionnaires. The association between gender and familial prevalence of hip dysplasia was presented as the prevalence proportions ratio (PPR), tested by χ2 test. Stratification was conducted for the variables age and operated hip side, with the Mantel-Haenszels analytical method, and tested for statistical significance by χ2. RESULTS: The familial prevalence of hip dysplasia in the study population was 30% (95% CI, 27%-34%), with 73% reporting affected first-degree relatives. Females have 32% increased risk of familial prevalence of hip dysplasia compared to males, but this difference in risk was not statistically significant (p = 0.10). CONCLUSIONS: The study shows that females have 32% increased familial prevalence of hip dysplasia compared to males, but the increased prevalence was not statistically significant probably due to the low power of the study.

Novel 31.2 kb α0 Deletion in a Palestinian Family with α-Thalassemia.

A previously unknown α(0) deletion, designated - -(DANE), was found in three generations of a Danish family of Palestinian origin. Six patients were heterozygous and three patients had deletional Hb H (ß4) disease with a compound heterozygosity for the common -α(3.7) (rightward) deletion. Multiplex ligation-dependent probe amplification (MLPA) supplemented by repeated polymerase chain reaction (PCR) amplification identified the 5' and 3' breakpoints in the α-globin gene cluster. This novel 31.2 kb deletion (NG_000006.1: g.8800_40007del31208) leads to the removal of the HBZ, HBA2 and HBA1 genes.

Association of CHRDL1 mutations and variants with X-linked megalocornea, Neuhäuser syndrome and central corneal thickness.

We describe novel CHRDL1 mutations in ten families with X-linked megalocornea (MGC1). Our mutation-positive cohort enabled us to establish ultrasonography as a reliable clinical diagnostic tool to distinguish between MGC1 and primary congenital glaucoma (PCG). Megalocornea is also a feature of Neuhäuser or megalocornea-mental retardation (MMR) syndrome, a rare condition of unknown etiology. In a male patient diagnosed with MMR, we performed targeted and whole exome sequencing (WES) and identified a novel missense mutation in CHRDL1 that accounts for his MGC1 phenotype but not his non-ocular features. This finding suggests that MMR syndrome, in some cases, may be di- or multigenic. MGC1 patients have reduced central corneal thickness (CCT); however no X-linked loci have been associated with CCT, possibly because the majority of genome-wide association studies (GWAS) overlook the X-chromosome. We therefore explored whether variants on the X-chromosome are associated with CCT. We found rs149956316, in intron 6 of CHRDL1, to be the most significantly associated single nucleotide polymorphism (SNP) (p = 6.81×10(-6)) on the X-chromosome. However, this association was not replicated in a smaller subset of whole genome sequenced samples. This study highlights the importance of including X-chromosome SNP data in GWAS to identify potential loci associated with quantitative traits or disease risk.

Eating behavior, prenatal and postnatal growth in Angelman syndrome.

The objectives of the present study were to investigate eating behavior and growth parameters in Angelman syndrome. We included 39 patients with Angelman syndrome. Twelve cases had a larger Class I deletion, eighteen had a smaller Class II deletion, whereas paternal uniparental disomy (pUPD) or a verified UBE3A mutation were present in five and four cases, respectively. Eating behavior was assessed by a questionnaire. Anthropometric measures were obtained from medical records and compared to Danish reference data. Children with pUPD had significantly larger birth weight and birth length than children carrying a deletion or a UBE3A mutation. We found no difference in birth weight or length in children with Class I or Class II deletions. When maternal birth weight and/or birth weight of siblings were taken into consideration, children with Class I deletion had a lower weight at birth than expected, and the weight continued to be reduced during the investigated initial five years of life. In contrast, children with pUPD showed hyperphagic behavior and their weight increased significantly after the age of two years. Accordingly, their body mass index was significantly increased as compared to children with a deletion. At birth, one child showed microcephaly. At five years of age, microcephaly was observed in half of the deletion cases, but in none of the cases with a UBE3A mutation or pUPD. The apparently normal cranial growth in the UBE3A and pUPD patients should however be regarded as the result of a generally increased growth. Eating behavior, pre- and postnatal growth in children with Angelman syndrome depends on genotype.

Best practice guidelines and recommendations on the molecular diagnosis of myotonic dystrophy types 1 and 2.

Myotonic dystrophy is an autosomal dominant, multisystem disorder that is characterized by myotonic myopathy. The symptoms and severity of myotonic dystrophy type l (DM1) ranges from severe and congenital forms, which frequently result in death because of respiratory deficiency, through to late-onset baldness and cataract. In adult patients, cardiac conduction abnormalities may occur and cause a shorter life span. In subsequent generations, the symptoms in DM1 may present at an earlier age and have a more severe course (anticipation). In myotonic dystrophy type 2 (DM2), no anticipation is described, but cardiac conduction abnormalities as in DM1 are observed and patients with DM2 additionally have muscle pain and stiffness. Both DM1 and DM2 are caused by unstable DNA repeats in untranslated regions of different genes: A (CTG)n repeat in the 3'-UTR of the DMPK gene and a (CCTG)n repeat in intron 1 of the CNBP (formerly ZNF9) gene, respectively. The length of the (CTG)n repeat expansion in DM1 correlates with disease severity and age of onset. Nevertheless, these repeat sizes have limited predictive values on individual bases. Because of the disease characteristics in DM1 and DM2, appropriate molecular testing and reporting is very important for the optimal counseling in myotonic dystrophy. Here, we describe best practice guidelines for clinical molecular genetic analysis and reporting in DM1 and DM2, including presymptomatic and prenatal testing.

Myoblasts generated by lentiviral mediated MyoD transduction of myotonic dystrophy type 1 (DM1) fibroblasts can be used for assays of therapeutic molecules.

BACKGROUND: Myotonic dystrophy type 1 (DM1) is the most common muscle dystrophy in adults. The disease is caused by a triplet expansion in the 3'end of the myotonic dystrophy protein kinase (DMPK) gene. In order to develop a human cell model for investigation of possible effects of antisense and RNAi effector molecules we have used lentiviral mediated myoD-forced myogenesis of DM1 patient fibroblasts. FINDINGS: Transduced fibroblasts show a multinuclear phenotype and express the differentiation marker myogenin. Furthermore, fluorescence in situ hybridization (FISH) analysis revealed a statistical significant increase in the amount of nuclear foci in DM1 patient fibroblasts after myogenesis. Finally, no nuclear foci were found after treatment with oligonucleotides targeting the repeat expansions. CONCLUSIONS: The abundance of nuclear foci in DM1 patient fibroblasts increase following myogenesis, as visualized by FISH analysis. Foci were eradicated after treatment with antisense oligonucleotides. Thus, we propose that the current cell model is suitable for testing of novel treatment modalities.

Limited phenotypic variation of hypocalcified amelogenesis imperfecta in a Danish five-generation family with a novel FAM83H nonsense mutation.

BACKGROUND. Autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI) is a disease with severe dental manifestations. OBJECTIVES. The aims were by means of a genome-wide linkage scan to search for the gene underlying the ADHCAI phenotype in a Danish five-generation family and to study the phenotypic variation of the enamel in affected family members. RESULTS. Significant linkage was found to a locus at chromosome 8q24.3 comprising the gene FAM83H identified to be responsible for ADHCAI in other families. Subsequent sequencing of FAM83H in affected family members revealed a novel nonsense mutation, p.Y302X. Limited phenotypic variation was found among affected family members with loss of translucency and discoloration of the enamel. Extensive posteruptive loss of enamel was found in all teeth of affected subjects. The tip of the cusps on the premolars and molars and a zone along the gingival margin seemed resistant to posteruptive loss of enamel. We have screened FAM83H in another five unrelated Danish patients with a phenotype of ADHCAI similar to that in the five-generation family, and identified a de novo FAM83H nonsense mutation, p.Q452X in one of these patients. CONCLUSION. We have identified a FAM83H mutation in two of six unrelated families with ADHCAI and found limited phenotypic variation of the enamel in these patients.

A novel missense mutation (G43S) in the switch I region of Rab27A causing Griscelli syndrome.

The autosomal recessive Griscelli syndrome type II (GSII) is caused by mutations in the RAB27A gene. Typical clinical features include immunological impairment, silver-gray scalp hair, eyelashes and eyebrows and hypomelanosis of the skin. Rabs help determine the specificity of membrane trafficking steps within cells. In melanocytes, the GTP-bound form of Rab27A associates with the membranes of mature fully-pigmented melanosomes through its geranylgeranyl group. Once attached, Rab27A recruits the downstream effector Melanophilin (Mlph) and the actin-dependent motor protein Myosin Va (MyoVa). The molecular Rab27A/Mlph/MyoVA tripartite complex, which links melanosomes to the peripheral actin network, is required to achieve melanosome transfer to surrounding keratinocytes in the epidermis. Here we report a novel homozygous missense mutation c.127G>A, p.G43S in exon 2 of the RAB27A gene of an Afghani GSII patient. Laser scanning confocal microscopy showed that the G43S mutation, which is located in the highly conserved switch I region of Rab27A, induces perinuclear localization of melanosomes in normal melanocytes, and fails to restore melanosomes to the actin-rich periphery in GSII melanocytes. Co-immunoprecipitation studies showed that Rab27A(G43S) fails to interact with its effector Melanophilin, indicating that the switch I region functions in the recruitment of Rab effector proteins.