Phenotypic effects of balanced X-autosome translocations in females: a retrospective survey of 104 cases reported from UK laboratories.
Females with balanced X-autosome translocations are a clinically heterogeneous group of patients in which X breakpoint position and replication behaviour may influence phenotypic outcome. This study reviewed all cases reported by UK cytogenetics laboratories over a 15-year period (1983-1997). Publication bias was avoided by reviewing all reported cases. One hundred and four female carriers were identified, 62 of who were probands. By reason for referral, these were: multiple congenital abnormalities and/or developmental delay (MCA/DD): 26 (42%); gonadal dysfunction: 22 (35%); phenotypically normal with or without recurrent miscarriage (NRM): 9 (15%); recognized X-linked syndrome: 5 (8%). The information obtained was compared with published data and with data from the authors' own laboratories of female patients with balanced autosome-autosome translocations (n=115). We concluded that: (1) MCA/DD cases were significantly over-represented compared to previous published data (P<0.005) and were more common than in female probands with balanced autosome-autosome translocations (P<0.05). (2) MCA/DD cases showed random breakpoint distribution along the X chromosome (P>0.05). MCA/DD cases with subtelomeric breakpoints at Xp22 or Xq28 were not always associated with deviation from the expected pattern of X-inactivation where this was known. De novo cases were significantly more likely to be assigned as MCA/DD than any other category (P<0.005). (3) Gonadal dysfunction (GD) was invariably associated with a 'critical region' breakpoint, Xq13-q26, (20/22 probands). However, 7/44 (16%) of patients surveyed had breakpoints within Xq13-Xq26 and proven fertility. (4) Recognized 'X-linked syndrome' cases were significantly under-represented (P<0.001) compared to previous published data.
Waters
J J
JJ
Regional Genetics Service, Birmingham Women's Hospital, UK. jonathan.waters@bham-womens.thenhs.com
Campbell
P L
PL
Crocker
A J
AJ
Campbell
C M
CM
D000015:Abnormalities, Multiple / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D002658:Developmental Disabilities / Q000235:genetics*; D005260:Female; D006058:Gonadal Disorders / Q000235:genetics; D006801:Humans; D007753:Laboratories; D008875:Middle Aged; D010641:Phenotype; D012189:Retrospective Studies; D014178:Translocation, Genetic; D006113:United Kingdom; D014960:X Chromosome