Expansion of the phenotypic spectrum associated with pathogenic missense variation in DHX16.

Pathogenic heterozygous variants in DHX16 have been recently identified in association with a variety of clinical features, including neuromuscular disease, sensorineural hearing loss, ocular anomalies, and other phenotypes. All DHX16 disease-causing variants previously reported in affected individuals are missense in nature, nearly all of which were found to be de novo. Here we report on a patient with neuromuscular disease, hearing loss, retinal degeneration, and previously unreported phenotypic features including mitochondrial deficiency and primary ovarian insufficiency, in whom a novel de novo likely pathogenic variant in DHX16 NM_003587.4:c.2033A > G (p.Glu678Gly) was identified. Furthermore, we conducted an in-depth literature review of DHX16's role in disease and utilized high-performing in silico prediction algorithms to compare and contrast the predicted effects of all reported disease-associated DHX16 variants on protein structure and function.

Axonal polyneuropathy and ataxia in children: consider Perrault Syndrome, a case report.

BACKGROUND: Perrault Syndrome (PRLTS) is a rare, autosomal recessive disorder that presents with bilateral sensorineural hearing loss in all patients and gonadal dysfunction in females. It has been linked to variants in CLPP, ERAL1, HARS2, HSD17B4, LARS2, and TWNK genes. All reported cases due to TWNK variants have included neurologic features, such as ataxia and axonal sensorimotor neuropathy. CASE PRESENTATION: A 4.5-year-old female presented to neuromuscular clinic due to ataxia. Neurological examination revealed truncal ataxia and steppage gait, reduced deep tendon reflexes, and axonal sensorimotor polyneuropathy. Auditory brainstem response testing revealed an uncommon type of sensorineural hearing loss known as auditory neuropathy/auditory synaptopathy (AN/AS) affecting both ears. Magnetic Resonance Imaging (MRI) revealed subtle cauda equina enhancement. Nerve conduction studies led to a provisional diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP), and intravenous immune globulin (IVIG) was initiated. The patient was unresponsive to treatment, thus whole exome testing (WES) was conducted in tandem with IVIG weaning. WES revealed a compound heterozygous state with two variants in the TWNK gene and a diagnosis of Perrault Syndrome was made. CONCLUSIONS: Perrault Syndrome should be considered in the differential for children who present with bilateral sensorineural hearing loss, axonal polyneuropathy, and ataxia. Further examination includes testing for ovarian dysgenesis and known PRLTS genetic variants.

AMFR dysfunction causes autosomal recessive spastic paraplegia in human that is amenable to statin treatment in a preclinical model.

Hereditary spastic paraplegias (HSP) are rare, inherited neurodegenerative or neurodevelopmental disorders that mainly present with lower limb spasticity and muscle weakness due to motor neuron dysfunction. Whole genome sequencing identified bi-allelic truncating variants in AMFR, encoding a RING-H2 finger E3 ubiquitin ligase anchored at the membrane of the endoplasmic reticulum (ER), in two previously genetically unexplained HSP-affected siblings. Subsequently, international collaboration recognized additional HSP-affected individuals with similar bi-allelic truncating AMFR variants, resulting in a cohort of 20 individuals from 8 unrelated, consanguineous families. Variants segregated with a phenotype of mainly pure but also complex HSP consisting of global developmental delay, mild intellectual disability, motor dysfunction, and progressive spasticity. Patient-derived fibroblasts, neural stem cells (NSCs), and in vivo zebrafish modeling were used to investigate pathomechanisms, including initial preclinical therapy assessment. The absence of AMFR disturbs lipid homeostasis, causing lipid droplet accumulation in NSCs and patient-derived fibroblasts which is rescued upon AMFR re-expression. Electron microscopy indicates ER morphology alterations in the absence of AMFR. Similar findings are seen in amfra-/- zebrafish larvae, in addition to altered touch-evoked escape response and defects in motor neuron branching, phenocopying the HSP observed in patients. Interestingly, administration of FDA-approved statins improves touch-evoked escape response and motor neuron branching defects in amfra-/- zebrafish larvae, suggesting potential therapeutic implications. Our genetic and functional studies identify bi-allelic truncating variants in AMFR as a cause of a novel autosomal recessive HSP by altering lipid metabolism, which may potentially be therapeutically modulated using precision medicine with statins.

Diagnosis of autism in a rare case of tyrosine hydroxylase deficiency: a case report.

BACKGROUND: Tyrosine hydroxylase deficiency (THD) is a rare movement disorder with broad phenotypic expression caused by bi-allelic mutations in the TH gene, which encode for tyrosine hydroxylase (TH) protein. Some patients with THD have improvement in dystonia with carbidopa-levodopa, a synthetic form of dopamine typically used in Parkinson's disease, and are considered to have dopa-responsive THD. THD has been found in 0.5-1 per million persons, although due to overlapping symptoms with other disorders and the need for genetic testing, prevalence is likely underestimated. Existing literature describes some patients with THD having intellectual disability, but comorbid autism spectrum disorder (ASD) has not been reported. CASE PRESENTATION: A nearly 3-year-old boy was referred to pediatric neurology due to hypotonia, delayed motor milestones, and expressive speech delay. Whole exome sequencing confirmed tyrosine hydroxylase deficiency, detecting a novel variant p.S307C first reported here. The child was treated with carbidopa-levodopa with an excellent response, resulting in improved balance, fewer falls, and improved ability to jump, run and climb stairs. He was determined to have dopa-responsive THD. Due to his delays in expressive speech, the boy also had an assessment with a developmental and behavioral pediatrician, who identified a pattern of social pragmatic speech delay, sensory sensitivities, and restricted interests, and determined that he met criteria for a diagnosis of ASD. CONCLUSIONS: While ASD can stand alone as a clinical diagnosis, it is also a cardinal feature of other genetically-based neurological disorders. To our knowledge, this is the first case that describes a patient with both disorders. Perhaps THD may be among the genetic disorders linked with ASD.

Genetic counselors' perspectives on population-based screening for BRCA-related hereditary breast and ovarian cancer and Lynch syndrome.

Early identification of those with BRCA-related Hereditary Breast and Ovarian Cancer Syndrome (HBOC) and Lynch syndrome has the potential for early cancer detection and/or prevention; as such, these conditions are considered Tier 1 genetic conditions by the U.S. Center for Disease Control and Prevention. Given the decreasing cost of genetic testing, population-based screening (PBS) for such conditions may be the next step toward cancer prevention. This study aimed to understand genetic counselors' perspectives toward offering PBS for the Tier 1 conditions BRCA-related HBOC and Lynch syndrome. An online survey was distributed to 3,609 members of the National Society of Genetic Counselors. A total of 367 individuals participated in the study. Fifty percent of respondents felt that PBS for inherited cancer should not be offered; 93.3% felt that the current healthcare system is unprepared for implementation of PBS. However, most respondents agreed that PBS should be implemented within the next 10 years. Attitudes toward offering PBS were associated with respondents' work setting, cancer specialization, and perceived preparedness (p's < 0.05). The most commonly reported barriers to the implementation of PBS were shortage of genetic professionals and lack of infrastructure. Data in this study provide evidence that infrastructural barriers and educational gaps of non-genetic professionals would need to be addressed before successful integration of PBS into the healthcare system.

Turner syndrome due to Xp22.33 deletion with preserved gonadal function: case report.

Turner syndrome (TS) is a chromosomal condition affecting 1 in 2000 females characterized by partial or complete loss of one of the X chromosomes. We describe an 11-year-old female who was recently diagnosed with TS. Karyotype revealed a deletion of the distal portion of chromosome X. Chromosome single nucleotide polymorphism (SNP) array revealed microdeletion of Xp22.33p22.12. Patient reached her menarche at age 11 years. Both the patient and her mother have short stature. Her mother, however, has a normal karyotype. This is one of few case reports of TS with microdeletion of Xp22.33 reported in the literature, with normal ovarian function and possible future transmission of the deletion to the next generations.

Cancer Susceptibility Genetic Testing in a High-Risk Cohort of Urban Ashkenazi Jewish Individuals.

Prior to 2013, genetic testing for Ashkenazi Jewish (AJ) individuals primarily consisted of the three-site BRCA1/BRCA2 AJ panel, full sequencing of BRCA1/2, or the Lynch syndrome mismatch repair genes. Multigene panel testing became more widely available in 2013, but limited data are available regarding the impact of multigene panel testing for AJ individuals. Here, we report the frequency of cancer susceptibility gene mutations in a cohort of 427 AJ individuals seen in the Cancer Risk Clinic at The University of Chicago. We found that 29% of affected and 37% of unaffected individuals carried a pathogenic mutation (32% of overall cohort), primarily known familial mutations in BRCA1/2. A minority of mutations were identified in non-BRCA1/2 genes and consisted mainly of AJ founder mutations in CHEK2, APC, and the mismatch repair genes. A panel of AJ founder mutations would have identified the majority (94%) of mutations in clinically actionable genes in both affected and unaffected patients. Based on recent cost-effectiveness studies, offering all AJ individuals a founder mutation panel may be a cost-effective cancer prevention strategy.