First Report of a Derivative Chromosome 13 with a Duplicated 11p15 Locus Associated with Silver-Russell Syndrome.

Silver-Russell Syndrome (SRS) is a disorder that is primarily characterised by intrauterine growth restriction which may occur asymmetrically or in whole, leading to a fetus being small relative to its gestational age. We present a female infant (proband) born in 2018 at a tertiary hospital in Muscat, Oman, with severe congenital anomalies. The proband carried a >25Mb duplication of the chromosomal 11p15-11pter locus of chromosome 13; creating a derivative chromosome 13 (der[13]) and was reported as 46,XX,der(13)add(11p15-11pter). A methylation-sensitive assay confirmed a diagnosis of SRS. Although the prognosis for SRS patients is generally good, the proband presented with a clinically severe phenotype culminating in death at the age of nine months. To the best of the authors' knowledge, this is the first report of a derivative chromosome 13 with a duplicated 11p15 locus in a patient with SRS.

A First-Case Report of Pycnodysostosis in an Omani Boy.

Here we reported on the genetic findings of a 9-year-old Omani boy with a rare inherited bone disorder. The patient's clinical features include dysmorphic facial features, short stature, and skeletal abnormalities. Exome sequence of the patient's deoxyribonucleic acid revealed a variant in the cathepsin K gene, which was confirmed by Sanger sequencing. These findings established the diagnosis of pycnodysostosis (PKND). To the best of the authors' knowledge, this case is the first case to be reported in the Gulf Cooperative Region of the novel PKND with molecular confirmation.

Spondylo-ocular Syndrome Due to a Novel Variant in XYLT2 in an Omani Patient.

Spondylo-ocular syndrome (SOS) is a rare autosomal recessive disorder and affects primarily ocular and spinal tissues. This case report presented an Omani child with a novel homozygous variant, c.2070 G > A (p.Trp690Ter) in XYLT2 associated with SOS for the first time. Oman and other Middle East countries have a high consanguine marriage rate. Our case report will increase knowledge of SOS syndrome to be able to provide genetic diagnosis and counseling for other family members and families as well as prenatal diagnostics for the future pregnancies.

A first case report of hypohidrotic ectodermal dysplasia from Oman.

This is a first case report of a patient with hypohidrotic ectodermal dysplasia from Oman, who was found to carry a mutation in the EDAR gene after candidate gene selection based on regions of homozygosity in his genome.

Rare NF1 microdeletion syndrome in an Omani patient.

Neurofibromatosis-1 phenotype combined with webbed neck and short stature in a young Omani patient was revealed to be due to a de novo germ-line heterozygous 1.7 Mb microdeletion at 17q11.2. This lead to the diagnosis of NF1 microdeletion syndrome.

Recessive mutations in SLC38A8 cause foveal hypoplasia and optic nerve misrouting without albinism.

Foveal hypoplasia and optic nerve misrouting are developmental defects of the visual pathway and only co-occur in connection with albinism; to date, they have only been associated with defects in the melanin-biosynthesis pathway. Here, we report that these defects can occur independently of albinism in people with recessive mutations in the putative glutamine transporter gene SLC38A8. Nine different mutations were identified in seven Asian and European families. Using morpholino-mediated ablation of Slc38a8 in medaka fish, we confirmed that pigmentation is unaffected by loss of SLC38A8. Furthermore, by undertaking an association study with SNPs at the SLC38A8 locus, we showed that common variants within this gene modestly affect foveal thickness in the general population. This study reveals a melanin-independent component underpinning the development of the visual pathway that requires a functional role for SLC38A8.

A new recessively inherited disorder composed of foveal hypoplasia, optic nerve decussation defects and anterior segment dysgenesis maps to chromosome 16q23.3-24.1.

PURPOSE: We have previously described two families with unique phenotypes involving foveal hypoplasia. The first family (F1) presented with foveal hypoplasia and anterior segment dysgenesis, and the second family (F2) presented with foveal hypoplasia and chiasmal misrouting in the absence of albinism. A genome-wide linkage search in family F1 identified a 6.5 Mb locus for this disorder on chromosome 16q23.2-24.1. The aim of this study was to determine if both families have the same disorder and to see if family F2 is also linked to the 16q locus. METHODS: Family members underwent routine clinical examination. Linkage was determined by genotyping microsatellite makers and calculating logarithm of the odds (LOD) scores. Locus refinement was undertaken with single nucleotide polymorphism (SNP) microarray analysis. RESULTS: The identification of chiasmal misrouting in family F1 and anterior segment abnormalities in family F2 suggested that the families have the same clinical phenotype. This was confirmed when linkage analysis showed that family F2 also mapped to the 16q locus. The single nucleotide polymorphism microarray analysis excluded a shared founder haplotype between the families and refined the locus to 3.1 Mb. CONCLUSIONS: We report a new recessively inherited syndrome consisting of foveal hypoplasia, optic nerve decussation defects and anterior segment dysgenesis, which we have abbreviated to FHONDA syndrome. The gene mutated in this disorder lies within a 3.1 Mb interval containing 33 genes on chromosome 16q23.3-24.1 (chr16:83639061 - 86716445, hg19).