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Partial trisomy 10q with mild phenotype caused by an unbalanced X;10 translocation
  1. T Mononen1,*,
  2. A Sharp2,*,
  3. M Laakso1,
  4. R-L Meltoranta1,
  5. A-K Valve-Dietz3,
  6. K Heinonen1
  1. 1Department of Clinical Genetics, Kuopio University Hospital, Kuopio, Finland
  2. 2Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury, Wiltshire SP2 8BJ, UK
  3. 3Department of Pediatrics, Kuopio University Hospital, Kuopio, Finland
  1. Correspondence to:
 Dr A Sharp, Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury, Wiltshire SP2 8BJ, UK; 
 asharp{at}hgmp.mrc.ac.uk

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Trisomy 10 has been detected in spontaneous abortions and prenatally.1 Although there are no reports of duplication of the whole long arm of chromosome 10, duplication of 10q21–qter has been found in a stillborn infant.2 Trisomy of more distal 10q is associated with a characteristic syndrome and has been described in many cases which almost always are familial,3,4 but patients with trisomy of the proximal or medial segment of 10q have been less often described.4

We report on a 4 year old girl with a de novo unbalanced X;10 translocation, karyotype 46,X,der(X)t(X;10) (q21.2;q11.2), who is thus trisomic for almost the whole long arm of chromosome 10. As her clinical phenotype is disproportionally mild in relation to the region of 10q trisomy, we hypothesised that preferential inactivation of the derivative X;10 chromosome with spreading of X inactivation into the 10q segment might account for this discrepancy between phenotype and genotype. We report results of investigations of late replication, a feature of the inactive X, and expression and sequence analysis of genes located on the translocated region of 10q, and discuss our results relative to previous reports of unbalanced X;10 translocations.

CASE REPORT

Clinical findings

The proband was the second child of a healthy 28 year old mother and 40 year old father, born at term after an uneventful pregnancy. Her birth measurements were low but appropriate for gestational age: weight 3230 g (25th centile), length 46.5 cm (3rd centile), and head circumference 33 cm (10th centile). Apgar scores were 9 at one minute and 9 at five minutes. There was no family history of repeated miscarriages, mental retardation, or malformation syndromes.

She was referred for neurological evaluation aged 2 years because of delayed speech development. She had hardly any expressive speech and her ability to understand spoken language was delayed …

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