Syndromes due to aneuploidy of gonosomes

Aneuploidy = loss (monosomy) or presence of 1 or more chromosomes in the genome of a cell.


 * Causes: division disorder ( nondisjunction ) of homologous chromosomes in the I. maturation division or chromatids in the II. I see division.

Turner syndrome

 * Karyotype 45,X ;
 * incidence of about 1/10,000 girls born;
 * diagnosis: already in the prenatal period ultrasound diagnosis is possible - the fetus is affected by extensive lymphedema mainly in the neck area, after their resorption the skin folds remain permanently visible - pterygia coli ;
 * signs: small height (100%) – up to 150 cm, wide chest (53%), low hairline on the neck, hypoplasia of nails (60%), pigmented nevi (63%), delayed sexual development, ovaries normally established, gradually however, it turns into fibrous bands, mostly sterility , absence of secondary sexual characteristics (genital dysgenesis – 100%), puberty disorder;
 * exceptionally congenital defects of internal organs;
 * frequent mosaics (46,XX/45,X; 45,X/46,XX/47,XXX).

Syndrome XXX (so-called Superfemale )
More detailed information can be found on the XXX Syndrome page .


 * Karyotype 47,XXX ;
 * incidence of about 1/1,000 girls born;
 * signs: no typical phenotypic manifestations, non-constant psychomotor retardation, irregular puberty, more frequent spontaneous abortions, limited fertility;
 * there is no increased incidence of congenital malformations above the population risk.

Klinefelter syndrome

 * Karyotype 47,XXY (other variants are also possible, e.g. 48,XXXY);
 * incidence of about 1/1,000 male births;
 * signs: affected boys usually without problems until adolescence, infertility (100%), eunuchoid features, small rigid testes, azoospermia, in all forms hypogenitalism (reduced genitals, 100%), gynecomastia (50%), male psychosexual orientation;
 * average intelligence, tall stature;
 * patients with three or more X chromosomes have more often associated congenital developmental defects of internal organs and more severe mental retardation.

XYY syndrome (so-called Supermale)

 * Karyotype 47,XYY ;
 * incidence of about 1/1,000 male births;
 * signs: body height over 180 cm, previously considered increased aggressiveness was not confirmed, sometimes mild mental retardation, slightly limited fertility.

Related articles

 * Syndromes due to aneuploidy of autosomes
 * Chromosomal aberrations
 * Numerical chromosomal aberrations
 * Indications for karyotype examination
 * Clinical genetics