Ring chromosome 6: case report and review.

A ring chromosome 6 was identified in an apparently healthy girl with short stature and microcephaly. Of 100 peripheral lymphocyte metaphases analyzed, chromosome 6 was replaced in 73% by a monocentric ring chromosome, in 10% by a dicentric, in 1% by a tricentric, and 3% by two rings. Thirteen other cells were 45,XX,-6, which may represent 46,XX,r(6)/45,XX,-6 mosaicism. The breakpoints were located on bands p24 or p25 and q26 or q27. Eight other patients with a ring chromosome 6 have been reported. The most characteristic findings in subjects with a ring chromosome 6 are mental retardation and eye and ear abnormalities, none of which were present in our patient.