American journal of medical genetics. Part C, Seminars in medical genetics
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Am J Med Genet C Semin Med Genet · Jun 2014
Cerebellar hypoplasia: differential diagnosis and diagnostic approach.
Cerebellar hypoplasia (CH) refers to a cerebellum with a reduced volume, and is a common, but non-specific neuroimaging finding. The etiological spectrum of CH is wide and includes both primary (malformative) and secondary (disruptive) conditions. Primary conditions include chromosomal aberrations (e.g., trisomy 13 and 18), metabolic disorders (e.g., molybdenum cofactor deficiency, Smith-Lemli-Opitz syndrome, and adenylosuccinase deficiency), genetic syndromes (e.g., Ritscher-Schinzel, Joubert, and CHARGE syndromes), and brain malformations (primary posterior fossa malformations e.g., Dandy-Walker malformation, pontine tegmental cap dysplasia and rhombencephalosynapsis, or global brain malformations such as tubulinopathies and α-dystroglycanopathies). ⋯ The category of CH, associated neuroimaging findings and clinical features may suggest a specific disorder or help plan further investigations and interpret their results. Over the past decade, advances in neuroimaging and genetic testing have greatly improved clinical diagnosis, diagnostic testing, recurrence risk counseling, and information about prognosis for patients and their families. In the next decade, these advances will be translated into deeper understanding of these disorders and more specific treatments.
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Genome-wide association studies, DNA sequencing studies, and other genomic studies are finding an increasing number of genetic variants associated with clinical phenotypes that may be useful in developing diagnostic, preventive, and treatment strategies for individual patients. However, few variants have been integrated into routine clinical practice. ⋯ The National Human Genome Research Institute (NHGRI) and the Wellcome Trust thus convened a workshop to consider the processes and resources needed to: (1) identify clinically valid genetic variants; (2) decide whether they are actionable and what the action should be; and (3) provide this information for clinical use. This commentary outlines the key discussion points and recommendations from the workshop.
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Am J Med Genet C Semin Med Genet · Aug 2013
ReviewEbstein anomaly associated with left ventricular noncompaction: an autosomal dominant condition that can be caused by mutations in MYH7.
Left ventricular noncompaction (LVNC) is a relatively common genetic cardiomyopathy, characterized by prominent trabeculations with deep intertrabecular recesses in mainly the left ventricle. Although LVNC often occurs in an isolated entity, it may also be present in various types of congenital heart disease (CHD). ⋯ Recent studies identified mutations in the MYH7 gene, encoding the sarcomeric β-myosin heavy chain protein, in patients harboring this specific phenotype. Here, we will review the association between Ebstein anomaly, LVNC and mutations in MYH7, which seems to represent a subtype of Ebstein anomaly with autosomal dominant inheritance and variable penetrance.
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Am J Med Genet C Semin Med Genet · May 2009
ReviewNon-identical monozygotic twins, intermediate twin types, zygosity testing, and the non-random nature of monozygotic twinning: a review.
Monozygotic twins (MZ) are rarely absolutely "identical." This review discusses the types of genetic/epigenetic and prenatal environmental post-zygotic mechanisms that cause discordance within such twin pairs. Some of these mechanisms--ranging from heterokaryotypia to skewed X-chromosome inactivation--may cause extreme discordance, but these extremes are merely the more emphatic examples of discordance that, to some degree, underlies the majority of MZ twin pairs. Because of the entrenched misconception that MZ twins are necessarily identical, many MZ twin pairs are mistakenly designated as dizygotic (DZ). ⋯ However, familial monozygotic twinning is more common than suggested by the literature. Seven new families are presented in an accompanying paper. Despite the difficulties and dangers of twin pregnancy (especially so for MC twins), human twinning persists, and continues to both challenge and fascinate parents, clinicians and geneticists.
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Am J Med Genet C Semin Med Genet · Aug 2006
ReviewBreaking difficult news in a newborn setting: Down syndrome as a paradigm.
Breaking the difficult news of an unexpected diagnosis to parents in the newborn setting is a common occurrence in genetic counseling. Many clinical geneticists and genetic counselors have had the challenge of delivering a postnatal diagnosis of Down syndrome to parents of newborns. Down syndrome is a common chromosome condition occurring in approximately 1 in 800 live births. ⋯ We propose a theoretical framework from which the informing interview can be planned and future outcome data can be measured. In this way, researchers of this theme can investigate the process, including the healthcare professionals' delivery of difficult news and make recommendations for continued improvement of the process. Our model can be generalized to breaking difficult news for a variety of other congenital conditions.