TURNER SYNDROME (XO)
Genetics
Generally sporadic; no older maternal age seen
Paternal chromosome more likely to be missing
Many mosiac patterns (including Y-chromatin)
Findings
Small-stature female
Absence of one SHOX gene (short stature homeobox; embryonic
regulation of skeletal system, especially arms and legs)
Abnormal GH–IGF receptor axis
Gonadal dysgenesis–streak ovaries in XO
Average IQ 90
Congenital lymphedema, residual puffiness over dorsum of fingers
and toes
Broad chest, wide-spaced nipples
Low posterior hairline; webbed posterior neck
Cubitus valgus (elbow) and other joint problems
Horseshoe kidney, and other renal defects
Cardiac:
Bicuspid aortic valve (number 1 cardiac anomaly)
Coarctation
Aortic stenosis, mitral valve prolapse