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Von Hippel−Lindau Syndrome
Published in Dongyou Liu, Handbook of Tumor Syndromes, 2020
Mosaicism may be present in both somatic cells and gonadal cells, or be found only in gonadal, or germline, cells. Individuals with germline mosaicism are unaffected, while those with somatic mosaicism may be unaffected or mildly affected. Nevertheless, an individual who is mosaic for a mutation in the VHL gene still has a 50% chance of passing on the mutation to an offspring.
Clinical genetics
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
In germline mosaicism, a proportion of the gametes in an individual has the same mutation, even though other cells in the individual may not. A gamete that has the mutation will produce a child with an inherited disease. In this scenario, even if neither parent has the mutation in their blood or other tissues, there is a risk of having another child with the same mutation and therefore disease.
Patterns of Inheritance: Mendelian and Non-Mendelian
Published in Merlin G. Butler, F. John Meaney, Genetics of Developmental Disabilities, 2019
Merlin G. Butler, Michael Begleiter, Shannon Lillis, Molly Lund, F. John Meaney
In some instances, a normal appearing parent can have more than one child affected with an autosomal dominant condition. A possible explanation may be germline mosaicism whereby a parent carries the autosomal dominant disease-causing gene in some percentage of their germ cells, but not in their somatic cells. Because the disease-causing gene is only present in the germ cells the parent is not affected with the condition but can pass the condition on to his or her children. Obviously, germline mosaicism has significant implications for recurrence risks in a family and for genetic counseling.
Parental germline mosaic transmission of 5p13.2 microduplication in two siblings of a Chinese family
Published in Journal of Obstetrics and Gynaecology, 2022
Qi Tian, Li-Li Xu, Dong-Zhi Li
5p13 microduplication is a known contiguous gene syndrome, described so far in variable sizes, from 0.25 to 13.6 Mb, containing a variable number of genes (Novara et al. 2013; Iourov et al. 2015). Clinically, the syndrome is characterised by developmental delay and intellectual disability with facial dysmorphism. The NIPBL is likely the major dosage sensitive gene for the phenotype. The present case is the first documentation of germline mosaicism for a 5p13 duplication. Germline mosaicism is a rare but important phenomenon which is most commonly seen with autosomal dominant and X-linked disorders, including osteogenesis imperfecta, neurofibromatosis type I and Duchenne muscular dystrophy (Trevisson et al. 2014; Yang et al. 2018). Germline mosaicism has also been observed in a number of chromosomal deletions (Nimmakayalu et al. 2013; Tang et al. 2019), but seldom been reported in duplication. Meyer et al (2012) reported an apparent de novo 281 kb duplication of chromosome 2p25.3 in two male half-siblings with autism transmitted through the mechanism of maternal germline mosaicism. Rahman et al. (2019) presented two siblings who were both impacted by a large terminal duplication (18.82 Mb at 7q34-q36.3) and a deletion (3.90 Mb at 15q26.3), with absence in both parents, implicating a possible germline mosaicism.
Germline mosaicism in a DMD family: incidental identification in prenatal diagnosis
Published in Journal of Obstetrics and Gynaecology, 2018
Germline mosaicism can occur with any inheritance pattern, but it is most commonly observed in autosomal dominant and X-linked disorders (Edwards 1989). A mosaic germline mutation is significant because it can be obscurely passed to offspring. Most individuals are unaware of a naturally occurring germline mutation until they have a child who is affected. Duchenne Muscular Dystrophy (DMD) is a severe X-linked neuromuscular disease with an incidence of approximately 1 in 3500 newborn boys. The DMD locus has a high mutation frequency: one-third of mutations are de novo, and two-thirds are inherited from carrier mothers (Lee et al. 2014). Instances of germinal mosaicism have been elucidated in DMD families on the basis of more than one affected offspring born to an apparently non-carrier parent (Bermúdez-López et al. 2014). Here we report on germline mosaicism in a DMD family incidentally identified in prenatal diagnosis by using chromosomal microarray analysis (CMA).
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
Mosaicism, or the presence of two or genetically distinct cell lines in an individual, can affect both somatic and germline cells. The developmental timing of a mutation not only influences type and percentage of affected cells, but also the expression of the disease (11). Germline mosaicism is apparent in family histories where multiple affected children are born to parents who are unaffected and not found to carry the disease-causing variant in tested tissues. While some variants are presumed de novo following parental testing, mosaicism remains a possibility due to the inability to assess all somatic tissues for the variant of interest. This can lead to inaccurate recurrence risks for future outcomes.