General Medical Information

Somatic Anomalies

Joe Leigh Simpson

45,X individuals not only are short (less than 4 feet 10 inches), but often they exhibit many features of Turner’s stigmata. No single feature of Turner’s stigmata is pathognomonic, but in aggregate a characteristic spectrum exists that is more likely to occur in those with a 45,X complement than in individuals with most other sex chromosomal abnormalities. Assessment of renal, vertebral, cardiac, and auditory function is obligatory.

The molecular basis for short stature in Turner’s stigmata is uncertain, although the distal X short arm has long been known to be integral for normal somatic development. Fisher suggested that absence of a specific DNA sequence may cause features of “Turner’s stigmata.” Sequence RPS4Y is present on the Y short arm, and homologous sequence RPS4X is present on the X. These sequences differ at only 19 of 263 amino acid residues. RPS4X is not inactivated; thus, monosomy X individuals would be deficient at this locus. Fisher believe the number of ribosomes per cell is reduced if a RPS4X sequence is lacking, as it is in monosomy X.