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Congenital Cranial Dysinnervation Disorder
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Most cases are sporadic, with no family history, but few cases of autosomal dominant, autosomal recessive, and X-linked recessive inheritance have been documented in the literature. Cytogenetic anomalies at loci 1p22 and 13q12.2-13 have been found, but no specific gene has been attributed to the disorder yet.
Basic genetics and patterns of inheritance
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
There are four basic inheritance patterns of human single-gene disorders. These include autosomal dominant and autosomal recessive inheritance, in which the mutant gene is on an autosome, and X-linked dominant and X-linked recessive inheritance, in which the mutant gene is on the X chromosome. Individuals can be heterozygous for a given gene, meaning that they have two different forms, or alleles, of the gene at the same locus on each of the two different chromosomes. Individuals can also be homozygous for a gene, in which the two alleles are identical. Males are said to be hemizygous with respect to genes on the X chromosome, since they have only one copy of the X.
Genetics in neonatal surgical practice
Published in Prem Puri, Newborn Surgery, 2017
In X-linked recessive inheritance, the condition affects almost exclusively males, and females can be carriers (Figure 22.11). The classic examples of such conditions are hemophilia A and B, Duchenne and Becker muscular dystrophy, and Hunter syndrome.
NYX-related Congenital Stationary Night Blindness in Two Siblings due to Probable Maternal Germline Mosaicism
Published in Ophthalmic Genetics, 2021
H. l. Scanga, A. Liasis, M. S. Pihlblad, K. K. Nischal
In this family, two male children with clinical and electrophysiologic evidence of cCSNB were hemizygous for a pathogenic, in-frame deletion of NYX notated c.339_353delTGAGCTGCGCCTGGC. This variant results in a loss of function consistent with other pathogenic variants of this gene and has been previously reported in association with cCSNB (5). Based on the X-linked recessive inheritance pattern of NYX, a mother of two affected males is presumed to be an obligate carrier for the pathogenic variant; however, in this family, maternal genetic testing of independent blood and saliva samples failed to detect the causative variant. Failure to identify the pathogenic variant in a mother of multiple affected children could have several explanations, including maternal mosaicism of the germline with or without somatic involvement, a de novo mutational event, technical or human error during sample collection and laboratory testing, or a non-biological relationship.
Complete congenital stationary night blindness associated with a novel NYX variant (p.Asn216Lys) in middle-aged and older adult patients
Published in Ophthalmic Genetics, 2021
Takaaki Hayashi, Yusuke Murakami, Kei Mizobuchi, Yoshito Koyanagi, Koh-Hei Sonoda, Tadashi Nakano
Three patients, a male proband II-1 (JU1175), his unaffected mother (I-1, JU1196), his affected uncle (patient I-2, JU1234), and his affected male cousin (patient II-2, JU1904) in a Japanese family were ophthalmologically examined at The Jikei University Hospital or Kyushu University Hospital (Figure 1b). The pedigree pattern was consistent with X-linked recessive inheritance. Comprehensive ophthalmic examination included decimal best-corrected visual acuity (BCVA), slit-lamp examination, funduscopy, fundus autofluorescence imaging (FAF) (Optos California, Optos PLC, Dunfermline, UK), and optical coherence tomography (OCT) (Cirrus, Carl Zeiss Meditec AG, Dublin, CA, USA, Spectralis SD-OCT, Heidelberg Engineering, Heidelberg, Germany). Full-field electroretinography (ERG) using a light-emitting diode built-in electrode (LE-4000, Tomey, Nagoya Japan) was recorded in accordance with the protocols of the International Society for Clinical Electrophysiology of Vision (8). A long-duration ERG with 100-ms stimulus duration was also recorded following previously reported protocols (9–11). The ERG responses of the patients were compared to age-matched control individuals (n = 4, mean age, 68 years) with high myopia (mean axial length, 30.18 mm).
Duchenne muscular dystrophy: an overview to the cardiologist
Published in Expert Review of Cardiovascular Therapy, 2020
Fabio de Souza, Caroline Bittar Braune, Ana Paula Cassetta Dos Santos Nucera
Duchenne muscular dystrophy (DMD), described more than 150 years ago, is the most common form of muscular dystrophy in children, affecting approximately one in 3,500/5,000 liveborn boys [1,2]. It takes part in a large group of pathologies called dystrophinopathies, which are caused by genetic changes in the gene that codes for dystrophin, a protein that plays a structural role in the cytoskeleton of muscle cells by connecting intracellular structures with the extracellular matrix [3]. Mutations related to the dystrophin gene occur in the short arm of the X chromosome (Xp21.1), which represents the largest known gene, composed of 79 exons [4,5]. Mutations causing a shift in the open reading frame result in the absence of dystrophin, leading to the DMD phenotype. With a X-linked recessive inheritance pattern, a mother with this mutation has a 50% chance of transmitting it to her male children. Although most DMD mutations are inherited, spontaneous mutations can occur in up to 30% of cases [6].