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Background Sirenomelia, also called mermaid syndrome, is a rare lethal multi-system congenital deformity with an incidence of one in 60,000–70,000 pregnancies. Sirenomelia is mainly characterized by the fusion of lower limbs and is widely associated with severe urogenital and gastrointestinal malformations. The presence of a single umbilical artery derived from the vitelline artery is the main anatomical feature distinguishing sirenomelia from caudal regression syndrome. First-trimester diagnosis of this disorder and induced abortion may be the safest medical option. In this report, two cases of sirenomelia that occurred in an white family will be discussed. Case presentation We report two white cases of sirenomelia occurring in a 31-year-old multigravid pregnant woman. In the first pregnancy (18 weeks of gestation) abortion was performed, but in the third pregnancy (32 weeks) the stillborn baby was delivered by spontaneous vaginal birth. In the second and fourth pregnancies, however, she gave birth to normal babies. Three-dimensional ultrasound imaging showed fusion of the lower limbs. Neither she nor any member of her family had a history of diabetes. In terms of other risk factors, she had no history of exposure to teratogenic agents during her pregnancy. Also, her marriage was non-consanguineous. Conclusion This report suggests the existence of a genetic background in this mother with a Mendelian inheritance pattern of 50% second-generation incidence in her offspring.

Pontocerebellar hypoplasia (PCH) is currently classified into 13 subgroups and many gene variants associated with PCH have been identified by next generation sequencing. PCH type 1 is a rare heterogeneous neurodegenerative disorder. The clinical presentation includes early-onset severe developmental delay, progressive motor neuronopathy, and cerebellar and pontine atrophy. Recently two variants in the EXOSC9 gene (MIM: 606180), NM_001034194.1: c.41T>C (p.Leu14Pro) and c.481C>T (p.Arg161*) were identified in four unrelated patients with PCH type 1D (PCH1D) (MIM: 618065). EXOSC9 encodes a component of the exosome complex, which is essential for correct processing and degradation of RNA. We report here two PCH1D families with biallelic EXOSC9 variants: c.239T>G (p.Leu80Arg) and c.484dupA (p.Arg162Lysfs*3) in one family and c.151G>C (p.Gly51Arg) in the other family. Although the patients studied here showed similar clinical features as previously described for PCH1D, relatively greater intellectual development (although still highly restricted) and normal pontine structure were recognized. Our findings expand the clinical consequences of biallelic EXOSC9 variants.

Hearing loss is the most common sensory deficit in humans with causative variants in over 140 genes. With few exceptions, however, the population-specific distribution for many of the identified variants/genes is unclear. Until recently, the extensive genetic and clinical heterogeneity of deafness precluded comprehensive genetic analysis. Here, using a custom capture panel (MiamiOtoGenes), we undertook a targeted sequencing of 180 genes in a multi-ethnic cohort of 342 GJB2 mutation-negative deaf probands from South Africa, Nigeria, Tunisia, Turkey, Iran, India, Guatemala, and the United States (South Florida). We detected causative DNA variants in 25 % of multiplex and 7 % of simplex families. The detection rate varied between 0 and 57 % based on ethnicity, with Guatemala and Iran at the lower and higher end of the spectrum, respectively. We detected causative variants within 27 genes without predominant recurring pathogenic variants. The most commonly implicated genes include MYO15A , SLC26A4 , USH2A , MYO7A , MYO6 , and TRIOBP. Overall, our study highlights the importance of family history and generation of databases for multiple ethnically discrete populations to improve our ability to detect and accurately interpret genetic variants for pathogenicity.

Bardet–Biedl syndrome is a rare autosomal recessive form of syndromic obesity which is characterized by retinal degeneration, obesity, polydactyly, cognitive impairment, and renal and urogenital anomalies. In this study, we used whole-exome sequencing (WES) to investigate the underlying mutations in four Iranian children from consanguineous families with a clinical diagnosis of Bardet–Biedl syndrome (BBS). In three out of four children, we identified one previously reported frameshifting variant in the BBS12 gene (c.265-266delTT, p.L89fs) and two novel nonsense variants in MKKS (c.1196T>G, p.L399X) and BBS7 genes (c.1636C>T, p.Q546X). In the other child, no mutations were detected in known genes for BBS. However, we identified a novel variant in the ALMS1 gene (c.10996delC, p.Q3666fs) indicative of Alström syndrome. All variants were interpreted as pathogenic according to American College of Medical Genetics and Genomics (ACMG) guidelines and confirmed through Sanger sequencing. In conclusion, our results not only expand the spectrum of mutations in BBS and ALMS1 genes but also accentuate the importance of genetic testing for differentiating BBS from Alström syndrome.

Recurrent pregnancy loss is newly defined as more than two consecutive miscarriages. Recurrent pregnancy loss occurs in <5% of total pregnancies. The cause in approximately 40–60% of recurrent pregnancy loss cases remains elusive and must be determined. We investigated two unrelated Iranian consanguineous families with recurrent pregnancy loss. We performed exome sequencing using DNA from a miscarriage tissue and identified a homozygous NOP14 missense variant (c.[136C>G];[136C>G]) in both families. NOP14 is an evolutionally conserved protein among eukaryotes and is required for 18S rRNA processing and 40S ribosome biogenesis. Interestingly, in zebrafish, homozygous mutation of nop14 (possibly loss of function) resulting from retrovirus-mediated insertional mutagenesis led to embryonic lethality at 5 days after fertilization, mimicking early pregnancy loss in humans. Similarly, it is known that the nop14-null yeast is inviable. These data suggest that the homozygous NOP14 mutation is likely to cause recurrent pregnancy loss. Furthermore, this study shows that exome sequencing is very useful to determine the etiology of unsolved recurrent pregnancy loss.

Cohen syndrome is an autosomal recessive disorder with the primary symptoms of mental deficiency, progressive retinopathy, hypotonia, microcephaly, obesity of midchildhood onset, intermittent neutropenia, and dysmorphic facial features. The syndrome has high phenotypic heterogeneity and is caused by loss-of-function mutations in the VPS13B gene. Here, we introduce a novel homozygous nonsense mutation (c.8698G > T, p.E2900X) in the VPS13B gene in an 11-year-old Iranian boy with major symptoms of Cohen syndrome. He also had mild anemia accompanied by positive antiphospholipid antibodies, the latter has never been previously reported in Cohen syndrome.

Background Limb‐girdle muscular dystrophy (LGMD) is a non‐syndromic muscular dystrophy caused by variations in the genes involved in muscle structure, function and repair. The heterogeneity in the severity, progression, age of onset, and causative genes makes next‐generation sequencing (NGS) a necessary approach for the proper diagnosis of LGMD. Methods In this article, 26 Iranian patients with LGMD criteria were diagnosed with disease variants in the genes encoding calpain3, dysferlin, sarcoglycans and Laminin α‐2. Patients were referred to the hospital with variable distribution of muscle wasting and progressive weakness in the body. The symptoms along with biochemical and EMG tests were suggestive of LGMD; thus the genomic DNA of patients were investigated by whole‐exome sequencing including flanking intronic regions. The target genes were explored for the disease‐causing variants. Moreover, the consequence of the amino acid alterations on proteins' secondary structure and function was investigated for a better understanding of the pathogenicity of variants. Variants were sorted based on the genomic region, type and clinical significance. Results In a comprehensive investigation of previous clinical records, 6 variations were determined as novel, including c.1354–2 A > T and c.3169_3172dupCGGC in DYSF, c.568 G > T in SGCD, c.7243 C > T, c.8662_8663 insT and c. 4397G > C in LAMA2. Some of the detected variants were located in functional domains and/or near to the post‐translational modification sites, altering or removing highly conserved regions of amino acid sequence. Causative variants linked with LGMD in an Iranian population.

Charcot-Marie-Tooth disease (CMT) is the most common hereditary neuropathy of the peripheral nervous system with a wide range of severity and age of onset. CMT patients share similar phenotypes which make it often impossible to identify the disease types based on clinical presentation and electrophysiological studies alone. In recent years, novel genetic diagnostic approaches such as whole exome sequencing (WES) has provided a ground for accurate diagnosis of CMT through identification of the disease-causing mutation(s). In the present study, that approach was effectively employed. Two unrelated large pedigrees with multiple affected cases of various pattern of inheritance (one autosomal dominant and one X-linked) were included. Clinical and electrophysiological data were obtained. DNA sample from each pedigree’s proband was subjected to WES. Data analysis was performed using an in-house developed pipeline, adopted from GATK and ANNOVAR. Candidate variant segregation was evaluated by PCR-based Sanger sequencing. A known but extremely rare (unreported in the Middle Easterners) mutation in BSCL2 (c.C269T:p.S90L) as well as a novel hemizygous variant in GJB1 (c.G224C:p.R75P) were identified and segregations were confirmed by Sanger sequencing. This study supports effectiveness of WES for genetic diagnosis of CMT in undiagnosed families.

Cataract is defined as opacity in the crystalline lens and congenital cataract occurs during the first year of life. Until now, mutations of more than 50 genes in congenital cataract have been reported with various modes of inheritance. Among them, HSF4 mutations have been reported in autosomal dominant, autosomal recessive and age-related forms of cataract. The inheritance patterns of these mutations depend on their mutational positions in HSF4: autosomal dominant or recessive mutations are respectively found either in a DNA-binding domain or in (or downstream of) hydrophobic repeats. Here we report a novel homozygous HSF4 mutation (c.521T>C, p.Leu174Pro) in two affected sibs of an Iranian consanguineous family using whole exome sequencing. The mutation is predicted as highly pathogenic by in silico analysis (SIFT, Polyphen2 and MutationTaster) and is not found in any of control databases. This mutation is located in a hydrophobic repeat of the HSF4 protein, which is consistent with the mode of inheritance as an autosomal recessive trait.

Warburg micro syndrome is an autosomal recessive disease where patients present with optic, neurologic and genital symptoms. Until now, four disease genes for Warburg micro syndrome, RAB3GAP1 , RAB3GAP2 , RAB18 and TBC1D20 , have been identified. Here, we report two novel homozygous RAB3GAP1 mutations (c.22G>T, p.Glu8* and c.1353delA, p.Pro452Hisfs*5) in two consanguineous families by whole-exome sequencing.