Clinical findings in a patient mosaic for a supernumerary ring chromosome 20

Austin-Ward, Enrique Daniel; Castillo, Silvia; Dragnic, Yuri; Sanz, Patricia; Salazar, Samuel; Knoll, Joan H.M.

doi:10.1002/(sici)1096-8628(20000320)91:3<171::aid-ajmg2>3.0.co;2-z

Cited by 10 publications

(10 citation statements)

References 12 publications

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“…Clinical symptoms of r(20) syndrome may be caused by a partial monosomy since a ring chromosome is thought to arise from deletions of telomeric regions (17). On the other hand, r (20) is sometimes identified as an extra chromosome besides two normal ones and hence gives rise to the clinical picture of a partial trisomy (18). This supernumerary r(20) causes multiple anomalies but no epilepsy, and the resulting syndrome should be differentiated from r (20) syndrome (Table 1).…”

Section: Discussionmentioning

confidence: 99%

Mosaicism and phenotype in ring chromosome 20 syndrome

et al. 2005

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Ring chromosome 20 [r(20)] syndrome is a rare chromosomal disorder characterized by epilepsy, mild to moderate mental impairment, and malformation. Patients generally show mosaicism in 1-100% of lymphocytes with r(20). We report here a patient with r(20) syndrome who exhibited mild phenotype with the small ratio of mosaicism (13%) with r(20). Although previous small-scale studies concluded that the mosaicism ratio was unrelated to clinical phenotype, our reassessment of all 57 reported cases has revealed that the ratio is significantly associated with age at seizure onset, intelligence quotient, and malformation, but not with the response of epilepsy to drug treatment. Our results provide important clinical information and prediction for r(20) syndrome.

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Section: Discussionmentioning

confidence: 99%

Mosaicism and phenotype in ring chromosome 20 syndrome

et al. 2005

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“…To our knowledge, 13 cases of supernumerary r(20) have been reported so far. Of these, 8 cases were ascertained postnatally [Callen et al, 1991; Blennow et al, 1993; Van Langen et al, 1996; Viersbach et al, 1997; Crolla et al, 1998; Austin‐Ward et al, 2000; Pinto et al, 2005] and 5 prenatally [Batista et al, 1995; Viersbach et al, 1997; Cotter et al, 2005; Kitsiou‐Tzeli et al, 2009].…”

Section: Discussionmentioning

confidence: 99%

“…Previously described patients with an extra r(20) showed varying degrees of phenotypic abnormality. Among these descriptions, the most frequently noted manifestations are growth and psychomotor retardation, low‐set ears, hands and feet anomalies, and micrognathia [Callen et al, 1991; Blennow et al, 1993; Batista et al, 1995; Van Langen et al, 1996; Viersbach et al, 1997; Crolla et al, 1998; Austin‐Ward et al, 2000; Pinto et al, 2005; Kitsiou‐Tzeli et al, 2009] (Table I). In our study, Patient 1 had intrauterine growth retardation associated with some facial dysmorphism.…”

Section: Discussionmentioning

confidence: 99%

“…A detailed molecular cytogenetic characterization is helpful and informative to evaluate with precision the size and the constitution of the SMCs. It has been described some similarities between some cases of extra r(20) whose ring chromosomes appeared similar in size by routine cytogenetic analysis [Austin‐Ward et al, 2000], but these studies did not perform a detailed molecular cytogenetic characterization of the ring chromosomes 20. Indeed, among the published cases of supernumerary chromosome 20, two studies described the breakpoints at molecular level by FISH (Table I) and only one study had used aCGH to characterize their origin and size [Baldwin et al, 2008].…”

Section: Discussionmentioning

confidence: 99%

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Chromosomal breakpoints characterization of two supernumerary ring chromosomes 20

Guediche¹,

Brisset²,

Benichou³

et al. 2010

American J of Med Genetics Pt A

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The occurrence of an additional ring chromosome 20 is a rare chromosome abnormality, and no common phenotype has been yet described. We report on two new patients presenting with a supernumerary ring chromosome 20 both prenatally diagnosed. The first presented with intrauterine growth retardation and some craniofacial dysmorphism, and the second case had a normal phenotype except for obesity. Conventional cytogenetic studies showed for each patient a small supernumerary marker chromosome (SMC). Using fluorescence in situ hybridization, these SMCs corresponded to ring chromosomes 20 including a part of short and long arms of chromosome 20. Detailed molecular cytogenetic characterization showed different breakpoints (20p11.23 and 20q11.23 for Patient 1 and 20p11.21 and 20q11.21 for Patient 2) and sizes of the two ring chromosomes 20 (13.6 Mb for case 1 and 4.8 Mb for case 2). Review of the 13 case reports of an extra r(20) ascertained postnatally (8 cases) and prenatally (5 cases) showed varying degrees of phenotypic abnormalities. We document a detailed molecular cytogenetic chromosomal breakpoints characterization of two cases of supernumerary ring chromosomes 20. These results emphasize the need to characterize precisely chromosomal breakpoints of supernumerary ring chromosomes 20 in order to establish genotype-phenotype correlation. This report may be helpful for prediction of natural history and outcome, particularly in prenatal diagnosis.

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“…Among these descriptions, the most frequently noted manifestations were growth and psychomotor retardation, low-set ears, hand and foot anomalies, and micrognathia. [32][33][34][35][36][37][38][39][40] In patient 2, 30 a supernumerary marker was found in 43% of amniocytes and fetal lymphocytes. At 15 months of age, except for obesity, her psychomotor development was normal and no dysmorphic features were noted.…”

Section: Systematic Reviewmentioning

confidence: 99%