A very rare case of a newborn with tetrasomy 9p and literature review.

BACKGROUND: Tetrasomy 9p is a rare genetic condition which usually results from a supernumerary isochromosome derived from the short arm of chromosome 9. Phenotypic findings include multiple congenital anomalies, facial dysmorphism, growth and developmental delays, and also vary according to the presence and degree of mosaicism. CASE: We report on a newborn with tetrasomy 9p who deceased in the newborn period. She had facial features including low-set and anteverted ears, hypertelorism, prominent nasal bridge, and microretrognathia. Bilateral ventriculomegaly, vermian hypoplasia and corpus callosum agenesis were detected on magnetic resonance imaging and double outlet right ventricle (tetralogy of Fallot type), secundum atrial septal defect, and persistent left superior vena cava were displayed by echocardiography. Microarray analysis revealed 38,584 kb tetrasomic region at 9p24.3p13.1. We also present a review of the literature suggesting that there is a recognizable phenotype for this condition and an assessment of cardiac manifestations based on the size and the localization of the breakpoints. CONCLUSIONS: We conclude that cardiac manifestations do not differ according to the localization of the breakpoint. Persistent left superior vena cava seems to be consistent with breakpoints distal to q12, but the present case is different from them by breakpoint p13.1.

Investigation of Genetic Causes in a Developmental Disorder: Oculoauriculovertebral Spectrum.

OBJECTIVE: Oculoauriculovertebral spectrum (OAVS) is a genetically and clinically heterogeneous disorder that occurs due to a developmental field defect of the first and second pharyngeal arches. Even though recent whole exome sequencing studies (WES) have led to identification of several genes associated with this spectrum in a subset of individuals, complete pathogenesis of OAVS remains unsolved. In this study, molecular genetic etiology of OAVS was systematically investigated. DESIGN/SETTING/PATIENTS: A cohort of 23 Turkish patients with OAVS, referred to Hacettepe University Hospital, Department of Pediatric Genetics from 2008 to 2018, was included in this study. Minimal diagnostic criteria for OAVS were considered as unilateral microtia or hemifacial microsomia with preauricular skin tag. The cohort was clinically reevaluated for craniofacial and extracranial findings. Molecular etiology was investigated using candidate gene sequencing following copy number variant (CNV) analysis. WES was also performed for 2 of the selected patients. RESULTS: Patients in the study cohort presented similar demographic and phenotypic characteristics to previously described patients in the literature except for a higher frequency of bilaterality, cardiac findings, and intellectual disability/developmental delay. CNV analysis revealed a possible genetic etiology for 3 patients (13%). Additional WES in 1 of the 2 patients uncovered a novel heterozygous nonsense variant in Elongation factor Tu GTP-binding domain-containing 2 (EFTUD2) causing mandibulofacial dysostosis with microcephaly (MFDM), which clinically overlaps with OAVS. CONCLUSION: Detailed clinical evaluation for any patient with OAVS is recommended due to a high rate of accompanying systemic findings. We further expand the existing genetic heterogeneity of OAVS by identifying several CNVs and a phenotypically overlapping disorder, MFDM.

A Revisited Diagnosis of Collagen VI Related Muscular Dystrophy in a Patient with a Novel COL6A2 Variant and 21q22.3 Deletion.

The genetic etiology of collagen VI related muscular dystrophies is heterogenous. Genomic deletions in one allele involving COL6A2 or both COL6A1 and COL6A2 unmasking a pathogenic variant in the second nondeleted allele have been described in the etiology. We aimed to report the clinical and molecular findings of a 13-year-old boy with ring chromosome 21 who presented to our clinic with easy fatigability, muscle weakness, and waddling gait. Phenotypic delineation along with chromosomal microarray analysis and DNA sequencing were performed. Affymetrix CytoScan Optima array platform and DNA sequencing revealed a 2,202 kb de novo deletion at 21q22.3, including COL6A1 and COL6A2, and a novel heterozygous variant at position c.2875G > A;p.(Glu959Lys) in COL6A2, respectively. Before his admission to our center, the patient was evaluated for hypotonia elsewhere when he was 15 months old. He was diagnosed with ring chromosome 21 on peripheral blood karyotype analysis; however, no further assessment was performed at that time. He had normal growth with mild dysmorphic facial features, distal laxity, gastrocnemius hypertrophy, proximal muscle weakness, increased lordotic posture with mild flexion contractures at the knees, and gait disturbance. Although the phenotype does not fit into classical Ullrich congenital muscular dystrophies, muscle magnetic resonance imaging (MRI) revealed a complementary pattern consistent with collagen VI related myopathies. Genetic testing confirmed the clinical diagnosis as well. This patient yet represents another example of the effect of large genomic deletions leading to recessive disorders through unmasking a pathogenic variant in the second nondeleted allele.

Further Phenotypic Delineation of Partial Trisomy 17q and Partial Monosomy 20q due to Rare t(17;20).

Copy number variations in subtelomeric regions of chromosomes 17 and 20 are associated with intellectual disability and various systemic manifestations. Microarray analysis allows identification of submicroscopic chromosomal abnormalities and is applicable to elucidate the etiology of cognitive impairment in approximately one-fifth of the cases. In the present study, we report on 3 male children from 2 sisters, who suffered from intellectual disability, facial dysmorphism, and epilepsy. Despite the initial suggestion of an X-linked inheritance, the condition was associated with 17q25.3 duplication and concomitant 20q13.33 deletion, as detected by microarray analysis. Coexistence of a deletion and a duplication suggests unbalanced segregation of a parental balanced translocation. Further investigations revealed maternal balanced translocations, which resulted in copy number aberrations in the children following unbalanced segregations. The work-up underlined the importance of genomic screening using microarrays as the first-tier diagnostic tool in intellectual disability, despite an apparent X-linked segregation in the pedigree.

A case of Woodhouse-Sakati syndrome with pituitary iron deposition, cardiac and intestinal anomalies, with a novel mutation in DCAF17.

Woodhouse-Sakati syndrome is a rare genetic syndrome caused by homozygous mutations of the DCAF17 gene. Several endocrine organs may be affected in the course of the disease. We present a new case with pituitary iron deposition, cardiac and intestinal anomalies, with a novel mutation in DCAF17 gene. An 18-year-old female was admitted because of delayed puberty and amenorrhea. Hormonal evaluation revealed combined hyper-hypogonadotropic hypogonadism. GH and IGF-1 levels were low without short stature. ACTH levels were high and cortisol levels were supranormal with the lack of clinical findings of cortisol excess or deficiency. Pituitary MRI indicated paramagnetic substance deposition in gland. On follow-ups, non-autoimmune, insulinopenic diabetes mellitus and secondary hypothyroidism emerged. Woodhouse-Sakati syndrome was diagnosed on the basis of consistent clinical context and subsequently a novel mutation in DCAF17 was detected.