This document discusses chromosomal abnormalities, including common abnormalities seen in children. It describes the normal human karyotype of 46 chromosomes consisting of 22 pairs of autosomes and one pair of sex chromosomes. It then discusses specific abnormalities including trisomy 21 (Down syndrome), trisomy 18, Turner syndrome, Klinefelter syndrome, and structural abnormalities involving deletions or duplications of chromosomal segments. For each condition, it provides the genetic basis and characteristic clinical features as well as treatment approaches when available.

1. CHROMOSOMAL ABNORMALITIES
 P.THIRUNAGALINGA PANDIYAN
M.Sc.,(N) , D.Pharm.,
School of Nursing
Madurai Medical College
Madurai

2. CHROMOSOMAL ABNORMALITIES
 Chromosomes are rod like condensations of chromatin.
 They become visible in the nucleus only during cell division.
 They occur in pairs one number of each pair comes from the
father and the other from the mother.
 Biochemically chromosomes are made up of DNA
(deoxyribonucleic acid) genetically they consists of genes.

3. CHROMOSOMAL ABNORMALITIES
In 1956 tijo and levan found only 46 chromosomes in the
normal human karyotype.
22 pairs of autosomes and one pair of sex
chromosomes.
XX in the female and XY in the male.
 The autosomes have been classified and divided on the
basis of length and certain morphological characters

4. CHROMOSOMAL ABNORMALITIES
 Group A - 1 to 3 Pairs
 Group B - 4 & 5 Pairs
 Group C - 6 to 12 Pairs
 Group D- 13 to 15 Pairs
 Group E - 16 to 18 Pairs
 Group F - 19 to 20 Pairs
 Group G - 21 to 22 Pairs
 X chromosomes is included in Group C
 Y chromosomes included in the GroupG

5. CHROMOSOMAL ABNORMALITIES
Non-disjunction
 By an error in nuclear division called "non-disjunction" a pair of
chromosomes may fail to separate and both are carried to one pole.
The resulting daughter cells contain an unequal number of
chromosomes, 45 or 47
Translocation
 Sometimes during nuclear division, a portion of one chromosome
breaks away and becomes attached for another which is not
homologous to the first.This is called translocation.

6. CHROMOSOMAL ABNORMALITIES
Deletion
A piece of a chromosome may become detached and lost
from the karyo-type resulting in the loss of one or more
genes. If the loss is severe, it may be incompatible with live
birth.
Duplication
Some genes may appear twice in the same chromosome.
This is called duplication.

7. CHROMOSOMAL ABNORMALITIES
Inversion
 Sometimes a chromosomal segment becomes inverted and then the
order of sequence of genes is altered.
Isochromosomes
 These are a special class of structurally abnormal chromosomes,
arising because of misdivision
Mosaicism
 The cells of the body are compounded of cells of two or more
genetically different chromosomal types.This can result by mutation
or nondisjunction either during embryo or later life.

8. GENES
 Genes are the units of heredity.
 They contain the heredity information encoded in their
chemical structure for transmission from generation to
generation.
 They affect development and function both normal and
abnormal.
 It is said we inherit about 50000 genes from the father and
50000 genes from the mother.

9. GENES
 Since genes are contained in the chromosomes, genes also
occur in pairs.
 If the genes comprising a pair are alike (AA) the individual
described as homozygous for that gene
 If it is different (Aa) the individual is described as hetrozygus.
 A gene is said to be dominant when it manifests its effect both
in the heterozygous and the homozygous state.
 A gene is said to be recessive when it manifests its effect only
in homozygous state.

10. GENOTYPE AND PHENOTYPE
The term genotype refers to the total genetic
constitution of an individual and the term phenotype to
the outward expression of the genetic constitution.
Taking ABO blood group systems
 Genotypes are AA, AB, BB, AO, BO, and OO
 Phenotypes are A, B, O

11. AUTOSOMAL DOMINANT DISORDERS
 Every affected child has one affected parent.
 Affected individual needs heterozygous for the given allele
 Males and females are equally affected
 There are affected individual in several generations
 Examples
 Marfan syndrome , Osteogenisis Imperfecta, Huntington chorea,
Polydactyl ,Neurofibromatosis, Retinoblastoma ,Polycystic kidney,
Achondroplasia.

12. AUTOSOMAL RECESSIVE DISORDERS
 Each parent of an affected individual is carrier.
 Affected individual needs homozygous for the given allele
 Males and females are equally affected
 Examples
 Cystic Fibrosis ,Sickle Cell anemia, Albinism , Phenyl ketonuria,
Thalassaemia ,Galactosomia, Alkaptonuria , Hirschprung
diseases,Microcephaly,Tay-Sac disease.

13. X-LINKED RECESSIVE DISORDERS
 Males affected almost exclusively
 Transmitted from female carriers ( mother ) to sons
 Affected males cannot transmit the condition to their sons
 Daughter not affected but carrier
 Examples
 Haemophilia, Hydrocephalus, Glucose 6 Phosphate deficiency,
Duchenne muscular dystrophy.

14. X-LINKED RECESSIVE DISORDERS

15. X-LINKED DOMINANT DISORDERS
Daughters are affected almost exclusively
Transmitted from male carriers ( father ) to daughter
Son not affected but carrier
Examples :
Hereditary Heamaturia, Orofacial Digital Syndrome ,
Incontinentia Pigmenti.

16. X-LINKED DOMINANT DISORDERS

17. COMMON CHROMOSOMAL
ABNORMALITIES IN CHILDREN

18. TRISOMY 21 - DOWN SYNDROME
Down syndrome is one of the best recognized and
the most common serious chromosomal disorder
which is usually caused by an extra copy of
chromosome 21 (Trisomy 21).
It is characterized clinically, by growth retardation,
varying degree of mental retardation and a
spectrum of somatic abnormalities including head
and facial features.
Down syndrome has an incidence of approximately
1:700 live births

19. TRISOMY – 21 ( DOWN SYNDROME )

20. CLINICAL FEATURES OF DOWN SYNDROME
 A flattened face, especially the bridge of the nose
 Almond-shaped eyes that slant up
 A short neck
 Small ears
 A tongue that tends to stick out of the mouth
 Tiny white spots on the iris (colored part) of the eye
 Small hands and feet
 A single line across the palm of the hand (Palmar crease)
 Small pinky fingers that sometimes curve toward the thumb
 Poor muscle tone or loose joints
 Shorter in height as children and adults

21. TRISOMY 18
 Trisomy 18, also called Edwards syndrome after the
physician who first described the disorder
 it is a rare chromosome abnormality that affects
approximately one in every 6,000-8,000 live births.
 These children have severe developmental delay, as well
as severe birth defects and health problems involving
nearly every organ system in the body.

22. CLINICAL FEATURES OF TRISOMY 18
 Low birth weight
 Weak cry, and startle to sound
 Feeding problems and fail to thrive
 Small head size, with a prominent back of the head (occiput)
 Their ears are usually low set and the opening of their eyes; their
nose and their mouth are small.
 Their sternum (breastbone) is typically short.
 Almost all babies with trisomy 18 have heart defects

23. TURNER SYNDROME
 Turner syndrome was first described in 1938 by Dr Henry
Turner
 Turner syndrome, a condition that affects only females, results
when one of the X chromosomes (sex chromosomes) is
missing or partially missing.
 Their sex chromosomes present as XO instead of XX
 This abnormal condition is due to non disjunction of the sex
chromosomes.

24. CLINICAL FEATURES OF
TURNER SYNDROME
 Failure to begin sexual changes expected during puberty — Due to
ovarian failure
 For most women with Turner syndrome, inability to conceive a child
without fertility treatment
 TREATMENT
 There is no cure for Turner’s syndrome. However, the symptoms can be
managed by the following:
 Growth Hormone
 Estrogen Replacement Therapy

25. KLINEFELTER SYNDROME
 Child with Klinefelter syndrome have one or two extra sex
chromosome(s).
 The affected are always boys and, instead of having an XY
chromosome pair, they have XXY or XXXY as their sex
chromosomes.
 The features of this condition include infertility, shrinkage of the
testicles, and development of breasts.
 Treatment of Klinefelter syndrome does not begin until the child is
older. Around 11 or 12 years of age, the child’s testosterone levels will
be measured. If the levels are low, they will be given testosterone
injections on a regular basis.

26. SUPER FEMALES
"Super females" - Females with 3 to 5 X-chromosomes (XXX,
XXXX, XXXXX) have been found.
 In general, the higher the number of X-chromosomes, the
greater the degree of mental retardation and congenital
abnormalities, e.g., underdeveloped external genitalia,
uterus and vagina.

27. STRUCTURAL ABNORMALITIES DISORDERS
 Some chromosomal abnormalities occur when a segment of a chromosome is
deleted or duplicated. These types of abnormalities can cause birth defects in
one or more organ systems. Some examples are as follows:
CRI-DU-CHAT SYNDROME:
Child with this condition have a cry that sounds like a cat.
They also may have intellectual disability and congenital heart defects.
There is no cure for this syndrome.
The intellectual disability is addressed through special education and
counselling.

28. STRUCTURAL ABNORMALITIES DISORDERS
FRAGILE X SYNDROME
 This is the second most common chromosomal cause of severe
intellectual disability, after Down syndrome.
 Other characteristic features include an elongated face, prominent jaw,
large ears, and, in boys, enlargement of the testicles. There may also be
behavioural and cognitive problems.
 There is no cure for Fragile X syndrome.
 Treatment is supportive, and may include education plans, measures to
reduce anxiety, and medications to manage associated psychiatric
disorders.

29. STRUCTURAL ABNORMALITIES DISORDERS
 ANGELMAN SYNDROME
 Infants with Angelman syndrome have intellectual disability, cannot speak, and
have problems with their motor development .
 Educational interventions, physical and occupational therapies, and speech
therapy are generally helpful.
 PRADER-WILLI SYNDROME
 This condition causes obesity, intellectual disability, lower than normal amounts of
testosterone in boys, testes that do not descend properly into the scrotum, and
muscles that are too relaxed in tone.
 There is no cure for this syndrome, but the physical symptoms can be managed.
Special education and speech therapy may also be helpful.

30. NURSING CARE OFTHE CHILDWITH
CHROMOSOMAL ABNORMALITIES
 Identify the defects as early as possible
 Explain correct genetic information to the parents and family
 Discuss the conditions of the child with family
 Refer the advice the parent and family to attend genetic
counselling
 Early diagnosis through appropriate genetic testing
 Encourage the parents to ventilate their feelings
 Give supportive care to the child as needed

31. THANK YOU