In this article we will discuss about:- 1. Introduction to Turner’s Syndrome 2. Origin 3. Indications for Suspecting Turner’s Syndrome 4. Features 5. Chromosome Patterns 6. Ullrich’s Syndrome 7. Pure Gonadal Dysgenesis 8. Incidence XYY-Males and Criminal Behaviour.
Introduction to Turner’s Syndrome:
Further clues to the nature of the sex- determining mechanism in human beings has come from studies of another sex-abnormality, Turner’s syndrome. In 1938, Turner first described this syndrome in post-pubertal females consisting of sexual infantilism, short stature, webbed neck, and cubitus valgus.
These are phenotypically females, but at adolescence the adult characteristics do not develop normally and they never reach functional maturity. Wilkins and Fleischmann (1944) described “Streak” gonads devoid of ovarian foll icles in such cases. Pollani (1954) and Wilkins (1954) demonstrated that most cases are chromatin negative whereas Ford (1956) described an XO karyotype in a patient affected wih Turner’s syndrome.
Origin of Turner’s Syndrome:
The most common chromosomal finding in Turner’s syndrome is 44 autosomes and only one X chromosome. These patients are chromatin-negative. They have no barr body.
‘XO’-constitution is caused by non-disjunction more commonly in spermatogenesis than in oogenesis.
On rare occasions, chromatin-negative patients with gonadal dysgenesis have a male sex chromosme constitution (46/XY). Another rare group of chromatin-negative patients have an XO/XY sex chromatin constitution. It has been described in women with streak gonads, in men with undescended testes and in intersexes.
Indications for Suspecting Turner’s Syndrome:
Also complete manifestation of X-linked traits in girls: e.g., color-blindness, hemophilia; Duchenne’s muscular dystrophy, agamma globulinemia, glucose-6P-dehydrogenase deficiency.
Features of Turner’s Syndrome:
1. Lymphedema of dorsum of the hand and feet and excess of skin in the neck.
2. Short stature, never more than 5′ and phenotypically females.
3. Nails are frequently small, narrow and set deep into the nailpit or are square with increased lateral curvature.
4. Webbed neck and a low posterior hairlines are seen.
5. Broad shield-like chest with widely spaced nipples and underdeveloped breasts.
6. Cubitus valgus — increased carrying angle of the arm is common.
7. Fourth metacarpal and metatarsal bones are short.
8. Congenital cardiac malformation is coarctation of the aorta.
9. Renal abnormalities such as horseshoe kidney, double pelvis and ureter or minor rotational malformations may secondarily occur.
10. Intellectual impairment is occasionally present.
11. Sexual infantilism becomes evident at the time of expected puberty:
i) Primary amenorrhoea.
ii) Usually underdeveloped breasts consisting mostly of fat.
iii) Scanty growth of axillary and pubic hair.
iv) External genitalia are infantile.
v) Uterus may be represented by a hard string in the midline.
vi) Dysgerminomas and gonadoblastomas are often found.
vii) Patients are infertile generally.
12. Color blindness is more common in patients than in normal woman.
13. Incidence of diabetes mellitus and congenital pyloric stenosis is higher than normal population.
14. Premature closure of epiphyses may occur.
15. Small uterus, ovary represented by fibrous streaks. Primordial follicles usually absent. Excretion of gonadotrophins is elevated after puberty.
Chromosome Patterns in Turner’s Syndrome:
(a) X-monosomy:
Patients with an XO sex complement make the largest proportion of cases with Turner’s syndrome. The mechanism of formation of XO sex constitution is speculative. Use of color-blindness and Xga blood type as markers has shown that most of the cases which could be analyzed had an X of maternal origin. Nevertheless, since mating that would reveal a paternally derived X chromosome are rare, the data are inconclusive
(b) XO/XX mosaicism:
Many patients with Turner’s syndrome have two different cell populations, one an XO sex constitution and the other a normal XX sex complement. Height sometimes normal, spontaneous menstruation, lymphedema at birth, webbing of neck less frequent; sometimes normal ova are found in XO/XX patients. In XO/XX/XXX, buccal smears reveal nuclei with no barr body or with one or two. In XO/XXX, two or no barr bodies are seen.
(c) Isochromosome X:
Sometimes a large metacentric chromosome resembling an extra No. 3 chromosome is found and one of the normal X-chromo- some is lacking. The extra chromosome is assumed to be an isochromosome for the long arm of the “missing” X-chromosome. Lymphedema at birth, webbing of the neck and congenital heart disease are less frequent. Barr bodies are larger and more numerous than normal.
(d) Partial loss of an X chromosome:
Partial deletion of the short arm of X chromosome and of long armhas been reported in a few patients with Turner’s syndrome.
(e) Ring X chromosome:
This chromosome seems to be found by simple deletion of parts of both the short and long arms of the X chromosome with a subsequent fusion of chromatid ends.
(f) Minute sex chromosome:
Probably deleted X and Y chromosomes. These are seen in association with gonadal dysgenesis.
Ullrich’s Syndrome:
Pollani (1961, 1962) has reported women with neck webbing and other anomalies of Turner’s syndrome, but with normal ovarian function and secondary sex characteristics. These women are of chromatin positive and have normal XX karyotypes.
Pure Gonadal Dysgenesis:
The instances of this are under Turner’s syndrome because patients exhibit sexual
infantilism, primary amenorrhoea, and “streak” gonads.
Sex chromosome complement may be XX or XY .
Incidence:
1. About one out of every 3,000 female births results in a child with chromatin negative XO Turner’s syndrome.
2. Chromatin positive Turner’s syndrome is one-quarter of this.
The incidence of Turner’s Syndrome is much lower than expected. One reason is probably that population surveys with buccal smears miss some of the chromatin-positive mosaics; another is that a high proportion is lost as spontaneous abortions.
XYY-Males and Criminal Behaviour:
The incidence of this type of abnormality (with XYY) in the newborn males is about 0.2 percent. It has been shown that XYY males are reproductively functional and more or less normal in outlook (in comparison to XY male).
XYY males are different from the XY males in the following ways:
1. XYY males are more criminal in behaviour than XY males and XYY males are mainly involved in the crimes against property.
2. Mean age of the first criminal conviction is 13.1 yrs. in case of XYY males, whereas it is about 18 yrs. for XY males.
3. XYY males generally do not commit any crime against their siblings.
4. XYY males poorly respond to the corrective measures taken against their crime.
It has been suggested that the antisocial behaviour of the XYY males is due to the extra Y-chromosome and the extra Y-chromosome also has some effect on the growth of the body.
