Cytogenetics and Cancer Research

Cri du chat syndrome is a kind of genetic disorder that occurs when a small part of chromosomal material is missing from a particular region on chromosome 5.
 

Overview of Cri du Chat Syndrome

In 1963, Dr. Jerome Lejeune first described Cri du chat syndrome. It is named for the cat-like cry made by the patients with this genetic disorder. In French, Cri du chat means “cry of the cat”. Or we can call this syndrome as “5p minus syndrome”. This is because there is small deletion of genetic material from the short “p” arm of chromosome 5 to cause this unusual genetic disorder.
 

Features of Cri du Chat Syndrome

There are many unusual features for the infants with Cri du chat syndrome.

i. Cat-like cry (the most classic feature)

ii. Unusual facial features

iii. Poor muscle tone (hypotonia)

iv. Small head size (microcephaly)

v. Mental retardation

vi. Low birth weight

vii. Slow growth

viii. Congenital heart defects

ix. Language difficulties

x. Delayed motor skill development

xi. Behavioral problems (childish)
 

Genetic Basis of Cri du Chat Syndrome

The high-pitched mewing cry during infancy is caused by defective development of the larynx (organ in the throat which produced voice). The deleted part of chromosome 5 is essential for normal development. As we all know, human have 46 chromosomes in every single cell of our body. At the same time, we should have two copies of chromosome 5. However, individuals with Cri du chat syndrome have lost a small part of chromosome 5. There is a small piece of material has been deleted from the “p” arm of one of the chromosome 5. On the other hand, the deleted chromosomal material consists of many important genes for normal development. Because of losing these essential genes, the larynx, brain and other parts of body cannot function normally. Generally, the deletion is sporadic (occurs irregularly).
 

Diagnosis of Cri du Chat Syndrome

Yet, the cat-like cry from children with Cri du chat syndrome will becomes less noticeable when they get older. Therefore, we can just identify and diagnose this syndrome if a child with younger age has this unusual mewing cry. Chromosome analysis or karyotyping can provide the definitive diagnosis of Cri du chat syndrome by staining the chromosome and examining them under a microscope. FISH (fluorescence in-situ hybridisation) is useful and effective to detect a small deletion in chromosome like Cri du chat syndrome.
 
Unfortunately, there is still no cure for this syndrome. Nevertheless, the medical experts can still provide the supportive care and development therapy to the patients to make the things better. Once the unusual features are under controlled, most of them can live normally.
 
In conclusion, although there is still no cure for Cri du chat syndrome, we can still lessen the symptoms by receiving the suitable therapy.
 
I have to apologise as I seldom to update this Cytogenetics and Cancer Research blog recently. I’m busying doing my final year project in University of Malaya. However, I will try my best to keep on updating the blog. Thanks!

Angelman syndrome (AS) was first described by Dr. Harry Angelman, who is an English physician. He noticed that there are 3 children under his care with similar developmental problems. They looked very happy and tend to flap their hands when excited. Therefore, Dr. Harry Angelman described these children in his paper called “Puppet Children” as these children’s characteristics just like the puppet.
 
Angelman Syndrome is now a familiar genetic disorder to most clinical geneticists and child neurologists in Cytogenetics. It is a recognizable syndrome which related to mental retardation and infantile seizures. Unlike Prader-Willi syndrome that I described last week, individual with Angelman syndrome is because the loss of maternally inherited region 15q11 – q13 of chromosome 15. Simple to say, the AS individual does not inherit the region 15q11 – q13 of chromosome 15 from his/her mother but only from father.

 
The Angelman syndrome clinical diagnosis is heavily dependent on the combination of some common behaviour like excessive laughter, apparent happiness with tremulous movements and gait ataxia (lack of coordination of muscle movement). Usually, the normal prenatal and birth history do not provides any clues in diagnosis of AS in Cytogenetics. CT scans, laboratory tests of blood and urine are usually normal including metabolic screening. Consequently, it is difficult for the clinical experts to encounter the AS especially when the child is less than 12 months of age. It is because the tremulous movements, ataxia and severe lack of speech may not be apparent during that time.
 
There are many common features of Angelman syndrome.

i. Severe speech deficit (usually absent speech)
 
ii. Mental retardation
 
iii. Microcephaly (small head)
 
iv. Seizures (convulsions in which AS patient’s body shakes rapidly and uncontrollably)
 
v. Developmental delay
 
vi. Feeding problems
 
vii. Hypopigmentation (the loss of skin color)
 
viii. Frequently drooling
 
ix. Tend to put objects in mouth
 
The facial features general physical appearances are generally normal for the individual of Angelman syndrome. As the child with AS growing up, the correct diagnosis may become evident when speech is essentially absent and the attempts at walking are compromised because of sever ataxia. In addition, the seizures will occur more frequently after 1 year of age.
 
In conclusion, the individual of Angelman syndrome may be hyperexcitable with excessive laughing, grabbing and pulling to engage others. They are just like the ‘Angels’ who always bring happiness to people. Usually, the parents may be the first to suggest the possibility of Angelman syndrome. Thus, earlier detection of this genetic disorder may help the children to overcome the learning problem through the assessment from the clinical experts.
 

My ultimate hope is this Cytogenetics and Cancer Research blog can really help in increasing the awareness of people about the genetic disorders and cancer.