Turners syndrome
kibaru

defination
• The condition is defined as the combination of
the characteristic phenotypic features
accompanied by complete or partial absence
of the second X chromosome with or without
mosaicism

Introduction
• Turner syndrome is one of the most
common chromosome anomalies in
humans
• This is one of the most common
monosomies in live born humans

• It represents an important cause of short
stature and ovarian insufficiency in
females.
• It is caused by loss of part or all of an X
chromosome

History
Turner described a syndrome consisting of
sexual infantilism, webbed neck, and cubitus
valgus in adult females
 Ullrich described an 8-yr-old girl with short
stature and many of the same phenotypic
features.

epidemiology
• The phenotype in Turner syndrome is
female
• It is characterized by short stature and
underdeveloped gonads

• The frequency at birth is 0.4/1,000 (i.e.,
1/4,000 live born females or 1/8,000 live
births) or 1/1,500-2,500 live born females.

• it occurs much more frequently in
spontaneous abortions.

• The frequency of the 45,X karyotype at
conception is about 3.0%
• but 99% of these are spontaneously aborted,
accounting for 5-10% of all abortuses.

pathogenesis
• Half the affected individuals have 45, X in their
lymphocytes.

• The other half have a variety of abnormalities
of one of their sex chromosomes and may be
mosaic.

Turner syndrome is a sex chromosome disorder
It is caused by loss of part or all of an X
chromosome

Types of chromosomal anomalies associated with
Turner syndrome are
a)●45,X – 45,X (monosomy X) is found in approximately 45
percent of live births with Turner syndrome

• The X chromosome is derived from the mother in two-thirds
of patients with Turner syndrome, and from the father in the
remaining one-third

• B) ●45,X mosaicism – More than one-half of all patients
with Turner syndrome have a mosaic chromosomal
complement this cell line mosaicism results from sex
chromosome nondisjunction occurring during post-zygotic cell
division .
• Mosaicism with a n...