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Sex-chromosome aneuploidy

Not a medical test — for research and educational use only

Yeliztli analyses consumer genotyping-array data (23andMe / AncestryDNA), which is not a clinical-grade test. Results are not diagnostic, are not clinically validated, and must not be used to make medical decisions. Array data is especially unreliable for rare, disease-causing variants. Always confirm any finding with an accredited clinical laboratory and discuss it with a qualified clinician or genetic counsellor before acting on it. See the Intended use & disclaimers page for the details and the evidence behind this warning.

This is an opt-in, sensitive screen

Because this result can be psychosocially significant, it stays hidden until you explicitly choose to view it. It never changes the sex recorded for your sample.

This module screens your genotype data for a signature consistent with XXY (Klinefelter syndrome).

What you'll see

A single result: possible XXY, manual review, no aneuploidy signal, or indeterminate (when probe coverage is insufficient), along with the supporting counts (heterozygous X calls and Y-probe presence). It is framed as a screen that requires clinical karyotype confirmation.

Good to know

  • This is a screen, not a diagnosis — a positive signal needs confirmation by clinical karyotyping.
  • From array genotypes, XXY is the only sex-chromosome aneuploidy reliably detectable. It cannot detect Turner syndrome (45,X) or XYY (those need different signal types), and XXX is indistinguishable from typical XX.
  • Minimum probe-count thresholds guard against false calls from stray probes, and discordant X/Y signals in the manual-review band are not reported as clean negative screens.
  • An unresolvable X dosage alongside a chromosome-Y signal returns manual review, not a negative. Some samples fall between the levels this screen can tell apart. When that happens and there is a chromosome-Y signal above the noise floor — including one too weak to meet the presence threshold — the screen withholds the negative rather than asserting one. It is explicitly not a positive finding either; the screen cannot tell. When enough chromosome-Y probes were typed to judge and no Y signal is found, the result stays a negative; when too few were typed to judge at all, the result is indeterminate. These are the same samples the app's sex inference also declines to resolve.
  • A negative stored before that rule existed does not outlive it. The next time such a sample's database is opened, the app re-screens it from the sample's own genotype data and replaces the stored result, so an earlier "no XXY signature detected" for one of these samples is not shown again. Results for every other sample are left as they are.