Dr Deepthi de Silva
|Dr Deepthi de Silva MBChB, MRCP is a Clinical Geneticist. She studied medicine at the University of Aberdeen and after general medical and paediatrics training, she followed specialist training in Clinical Geneticist in Aberdeen, Scotland and is an accredited consultant in this field.
She has 29 peer reviewed indexed publications, three chapters and more than 240 citations of these publications.
She works as the Clinical Geneticist to the multidisciplinary cleft clinic at the Lady Ridgway hospital, Colombo. This clinic has a large case load of around 25 to 30 new cleft cases a month with cases coming from across the country. Many complex syndromic cases are referred to this clinic by members of the cleft team and other consultant colleagues.
Dr Deepthi de Silva’s main clinical interests are the orofacial malformation and other multiple congenital anomaly syndromes. She is also involved in developing cost effective genetic testing in Sri Lanka and the psychosocial impact and attitudes towards genetic diseases and their management.
Dr de Silva is currently attached to the department of Physiology, Faculty of Medicine, University of Kelaniya where she is a senior lecturer. She teaches and examines both undergraduate and post graduate students in physiology at the medical faculty, University of Kelaniya and at the post graduate institute of medicine, University of Kelaniya. She is an active member of the physiological society of Sri Lanka (PSSL) and has been its president in 2014. She is a vice president of the South Asian association of Physiologists (SAAP).
01 Who gets genetic diseases?
It is estimated that up to 5% of the population have a genetic disease. These could affect patients at different ages.
For example babies may be born with one of more malformations affecting their body such as congenital heart defects, cleft lip or palate or club foot. Some children have no such malformations but they may be found to develop a disease as they become older such as seizures, difficulty with reaching normal developmental milestones (such as starting to talk or walk at the normal time) or have complex conditions diagnosed such as autism. Others children may have been able to develop in the usual way for the first few years but later develop a disease which progressively worsens with time. Adults of varying ages may also develop genetic diseases including some inherited cancers and neurological diseases.
Clinical geneticists are involved in the care of patients from even before birth to adults including the oldest members of a family.
02 What types of conditions are referred to a clinical geneticist?
- Chromosomal diseases
- Single gene diseases
- Familial cancer syndromes
- Congenital malformations Diseases with an inborn error of metabolism
- Learning difficulties
- Disorders of growth
- Visual loss Hearing loss/ deafness
- Dysmorphic syndromes
03 Important Aspects
Asking questions from the doctor
Clinical geneticists offer information and discuss very complex issues with people who have or are at risk of having a child affected with a genetic disease. Many aspects of the appointment will involve areas that are scientifically complicated and therefore, you should not be embarrassed about asking for more information or explanations. Clinical geneticists across the world are used to this and in this clinic we will be happy to explain again aspects that are difficult to understand.
Clinical genetics is based on the absolute principle that the information that an individual or family give will be treated with confidentiality. It will not be discussed with any other family members or medical professionals without your knowledge and consent. The medical records and photographs are stored separately and safely and only available to the doctor looking after you.
This means that the clinical geneticist looking after you will try to help you come to a decision about what you/ your family should do regarding difficult decisions. These decisions may include deciding whether to have another pregnancy that may also be affected with a genetic disease or to have genetic testing performed (e.g. to have a carrier test to find out if you could pass a genetic disease to your child or whether to test your unborn child). Clinical geneticists across the world have adopted this position as we know that the decision that one person makes and is comfortable with is often different from that made by their own brother or sister. Decisions that people make vary according to many factors such as their own life experience, religious beliefs, financial position and family circumstances among others. There are often no correct or wrong decisions; only what works best for you and your family and clinical geneticists are able to help you to decide on this.
What happens at a genetic clinic?
An individual or family may be referred to a genetic clinic because the doctors looking after them suspect that there is or might be a genetic component to an illness. The genetic clinic appointment is there to attempt to identify if this is the case. You will be expected to bring all the relevant medical records including scans and any other investigations to the appointment.
All doctors follow a method to reach a diagnosis of a disease. This involves four steps namely taking a history, examination, investigations and treatment/ management.
There are some differences between other medical appointment and a visit to the genetics clinic. The questions that will be asked include taking your family history in detail and performing an examination looking for some rare features that help with reaching a diagnosis. In some patients, their height and other body measurements will be taken. Photographs are taken of some patients and the reason to be included as part of the medical record about the person who has been seen. In some cases a request will be made for showing the photographs to another doctor as a aid to diagnosis or occasionally to teach medical students or doctors. You have a right to refuse to have your photograph taken or used for any other purpose than what you agreed and your request will be respected.
Families are encouraged to discuss specific issues regarding the diagnosis of a genetic disease and obtain information they need to make decisions about investigations that need to be done for diagnosing the condition.
Once a diagnosis is made, a discussion will follow regarding what it means for the future care of the affected person as well as what implications there may be for the condition happening again in another family member. Your doctor will also be informed (with your consent) of the diagnosis and the discussion that followed.
You may also be asked to discuss the diagnosis with other family members and sometimes ask them also to visit the genetic clinic. In some cases this is not possible, and if this is the case with your family, you should tell this to the doctor.
Genetic testing is carried out for many different reasons the main ones being as follows.
01Diagnose a suspected condition
02Identify healthy individuals who are carriers (and have a risk of having a child affected with a disorder)
03Pre symptomatic diagnosis (to identify people who will develop a disease later in life)
04Prenatal diagnosis (identify pregnancies at risk of a genetic disease)
05Pharmacogenetics: identify people who are likely to respond well or adversely to a specific treatment.
06Cancer genetics: tests are performed in some patients to decide on the type of their cancer and the need for specific therapies
07Some people are at risk of an inherited predisposition to cancer and genetic testing for this could be included in either (1) or (3) above.
08Some laboratories are offering genetic screening to decide if a person is at risk of developing a host of different diseases using whole genome screening (see below) for healthy individuals.
01 What are the costs of genetic testing? (monetary and psychological)
02 Are there any other issues with genetic testing?
Types of testings
There are many different types of genetic testing making this a very complex area that is also rapidly changing.
Confirm or refute a suspected genetic diagnosis
Traditionally genetic testing was used for either confirming or excluding a diagnosis that the doctors suspected in a patient. This type of testing could be to confirm or exclude a known chromosomal or single gene disorder. A more recent innovation is the introduction of ’gene panels’ where the genetic sequence of multiple genes associated with a specific disease (such as the large number of genes involved with cardiomyopathies or brain malformations) can be performed simultaneously and speed up the diagnostic process.
Genetic testing without a specific diagnosis
The second group of tests are performed to look for a genetic disease without knowing the exact diagnosis. This could involve a test for a chromosome abnormality (karyotype or microarray) or a gene level abnormality. The gene level abnormalities are detected by tests that are very complex and novel. These includes a test called whole exome sequencing (WES) that looks at at the DNA sequence of around 1% of our genome. In other words, the sequence of all the exons of the expressed genes of the body is sequenced and the data interpreted using computer software that looks for variations from the expected and determines the likelihood of a disease being caused by a specific DNA sequence change. Once a DNA alteration is found, careful clinical review is essential to determine if the anomaly is the likely cause of the problems in the patient.
A more complex test than WES is called whole genome sequencing where, as the name suggests, the DNA sequence of all the genes in a person is obtained. There is a higher chance of picking up an abnormality but errors caused by the large size of data generated are also possible. It is essential that expert review of the DNA data is made with the input of a clinical geneticist familiar with the patient.
Role of research in Clinical Genetics
Clinical genetics has seen a massive amount of change with regard to knowledge that is available regarding the causes of human diseases. This information was generated by doctors and scientists researching in to the cause of diseases. Data collected previously have helped enormously in the identification of rare diseases and this would not be possible without the active cooperation of families and patients affected with genetic disease from across the world.
At present, the availability of newer molecular methods such as whole genome sequencing and the rapidly reducing cost of such testing means that more families affected with genetic disease may benefit from these investigations.
You may be asked to help with research projects in to rare genetic diseases in Sri Lanka or abroad. If this is the case, you will be given written information about the research project and you can decide on whether to be involved or not. You will be expected to sign an consent form. Please remember that you can choose not to be involved in research and if this is the case, the care given to you or your child will not be affected by your decision.
How can I get an appointment at the genetic clinic?
- You need to be referred by a consultant to the genetic clinic.
- Appointments can be given at the Lady Ridgway hospital room 35 (telephone number) or the Department of Physiology, Faculty of Medicine, University of Kelaniya, Ragama (tel 011 291128).
- You will be expected to bring all the relevant medical records including scans and any other investigations to the appointment.