Isochromosome Xq
46,X,i(X)(q10)
Also known as: i(Xq), isochromosome X
46,X,i(X)(q10) pairs one normal X with an isochromosome of the X long arm, so the short arm of the X is present in only one copy. It is a recurrent structural cause of Turner syndrome.
Open in the interactive visualizer →
What the notation means
46- total chromosome count (the normal human number)
X- sex chromosomes: one X, listed alone because the other X is named in the rearrangement below. This is not monosomy X
i(X)(q10)- an ISOCHROMOSOME i(X): a mirror-image chromosome made of two long (q) arms, so the short (p) arm is lost; you end up with 3 copies of one arm and 1 of the other. Expected X inactivation is skewed: the structurally abnormal X is silenced and the normal X stays active, the pattern that leaves the least functional imbalance. That depends on the abnormal X keeping its X-inactivation center at Xq13
Clinical notes
Turner syndrome (45,X and variants)
Loss of all or part of the second sex chromosome. 45,X (monosomy X) is classic; variants include an isochromosome i(Xq), a ring r(X), an idic(Y), and 45,X mosaicism (e.g. 45,X/46,XX). Short stature, ovarian dysgenesis/streak gonads, webbed neck, coarctation/bicuspid aortic valve, lymphedema.