A ring X chromosome, 46,Y,r(X)(p22.33q28), as a cause of extreme short stature in a male.

We describe a 15 10/12-year-old boy (Tanner stage 4, peak growth velocity 7 cm/year) with a ring X chromosome who presented with extreme short stature (mean -5.3 SD) as the sole recognizable abnormality. His chromosome constitution was determined to be 46,Y,r(X)(p22.33q28) in 174 of 182 peripheral blood cells and in 35 skin fibroblasts. Of the remaining eight peripheral blood cells, five had a dicentric double-size ring and three had a smaller ring. Other laboratory studies for short stature were noncontributory. We suspect that the ring's specific behavior in mitosis or its effect on expression of the statural determinant on the X chromosome short arm may be responsible for short stature in this patient.