Directory of services
Clinical Genetics Service
The mission of Clinical Genetics is to provide a comprehensive clinical and diagnostic genetics service to the local and regional area. Patients and their families are assured of receiving efficient and compassionate care of the highest standard in an environment that respects the rights, beliefs, and dignity of each patient and family.
SCOPE OF SERVICE
In clinical genetics an accurate diagnosis is of paramount importance since genetic counseling based on an incorrect diagnosis can have devastating results for a patient or family.
The steps taken to reach a diagnosis include taking a detailed family history, carrying out a physical examination for dysmorphic features, referral of the patient to other clinical services for evaluation, requesting relevant laboratory, radiological, and other investigations, and reviewing past medical records. When the results of all evaluations and investigations are available a clinical geneticist analyzes the data in order to reach a diagnosis.
In some cases the patient may have a unique, previously un-described disorder. In such instances the family history is very important. Parental consanguinity, the occurrence of the disease in both or either sexes, and affected relatives in more than one generation all provide clues to the possible mode of inheritance of an unknown disorder. With a detailed family history and careful analysis of the data it is possible to counsel families and give a probable recurrence risk figure even in the absence of a specific diagnosis.
While many individual genetic disorders are rare, as a group they account for considerable morbidity and mortality, especially among pediatric patients. It is important to be aware of the wide spectrum of disorders that have a genetic basis and of the need to refer patients for evaluation by a clinical genetics service.
- The clinical genetics service provides care for both pediatric and adult patients.
Prior to conception or when a couple is planning marriage there are a number of factors that might lead a physician to conclude that a woman or couple could benefit from a consultation. The reasons for referral include the following:
- A positive family history of a genetic disorder (e.g., fragile X syndrome, muscular dystrophy, cystic fibrosis) and concern about its recurrence.
- Previous infertility or sterility problems.
- Exposure to potential teratogenic or mutagenic agents e.g., valproic acid, phenytoin, ACE inhibitors etc.
- Maternal health (e.g., diabetes, phenylketonuria, epilepsy).
- Consanguineous marriage.
- Two or more prior miscarriages or pregnancy losses.
- A previous stillborn child.
- A previous child with a genetic or chromosomal disorder or birth defect (e.g., neural tube defect, Down syndrome, phenylketonuria).
- Sickle cell trait/disease, alpha or beta-thalassemia trait.
The Clinical Genetics Service provides preconception or premarital counseling with the aim of providing couples with the information necessary to make informed decisions about reproduction and the available testing, intervention, or treatment options.
For example, individuals who carry a balanced chromosome rearrangement should be offered the option of prenatal diagnosis in future pregnancies and women who are using teratogenic agents should be counseled about the associated risks.
The advantage of preconception or premarital counseling is that it is possible to pursue genetic studies prior to marriage or pregnancy. In the absence of time constraints, a tiered evaluation can be done. Medical records can be requested and reviewed, laboratory tests can be ordered and analyzed systematically, and extended family studies can be undertaken as needed.
During pregnancy, tests are available that can determine whether or not the fetus has a chromosome abnormality, certain single gene disorders, or structural abnormalities. Women who might benefit from prenatal diagnostic tests and counseling include the following:
- Women who will be 35 years or older at delivery.
- A woman and/or her husband who are known to carry the same mutated gene that can cause a genetic disorder in a child (e.g., sickle cell anemia, cystic fibrosis, Marfan syndrome).
- woman or her partner who are known to carry a chromosome rearrangement or abnormality.
- Couples with a family history of a neural tube defect.
- Couples with a previous child born with multiple congenital anomalies or a chromosome abnormality.
- Women with an abnormal level of maternal serum alpha fetoprotein (AFP), humanchorionic gonadotrophin (hCG), or estriol (uE3).
- Women exposed to an infectious disease, radiation, drugs, or other environmental agents during pregnancy.
Many single gene disorders can be diagnosed prenatally. Consultation with a clinical geneticist will provide up-to-date information regarding prenatal genetic testing. Preimplantation genetic testing is also an option for some couples.
Women who are exposed to teratogenic agents during pregnancy may also benefit from genetic counseling. In some instances, the risk of an abnormality may be much lower than first assumed and counseling may reduce maternal anxiety. In some cases, further diagnostic studies may be proposed to assess fetal development, or to rule out the presence of obvious structural defects associated with exposure to a specific agent. Only rarely are the risks of a birth defect high enough to make pregnancy termination a reasonable option.
Infant and Child Patients
Factors that might lead a physician to conclude that an infant or child could benefit from a genetic evaluation include the following:
- A history of intrauterine growth retardation or failure to thrive.
- Abnormal growth patterns (short stature, obesity, excessive growth).
- Ambiguous or abnormal genitalia, early onset of puberty.
- Microcephaly, macrocephaly or craniosynostosis.
- Psychomotor delay or mental retardation.
- Hypotonia, hypertonia.
- A parent, sib or other relative who has problems similar to those observed in the patient.
- Abnormal or unusual facial features.
- Abnormal body and limb proportions, asymmetry.
- Major or minor congenital anomalies.
- Metabolic disorder.
- Muscular weakness.
- Bleeding tendency.
- Blindness or deafness.
- A significant regression in developmental progress.
- An unusual body odor.
- Excessive unexplained vomiting.
- Unusual behavior, especially when associated with minor malformations (hand biting, hand flapping, autistic symptoms, abnormal sleep patterns, etc).
Major malformations are usually noted at delivery or shortly after birth, and a genetic consultation requested prior to discharge from the hospital. In some cases, establishing a diagnosis in the newborn period may be critical if informed decisions are to be made about surgery or the degree of medical intervention provided to sick babies.
Adolescent and Adult Patients
Some reasons for adolescent and adult referrals for a genetic evaluation and counseling are:
- Abnormal sexual maturation.
- Amenorrhea (failure to menstruate), delayed puberty.
- Growth retardation.
- Excessively tall stature (e.g., Marfan syndrome).
- A diagnosis of an adult onset genetic disease (e.g., Huntington disease, myotonic dystrophy).
- A positive history of familial disorders (e.g., colon cancer, breast/ovarian cancer, familial hypercholesterolemia, psychiatric or behavioral disorders).
- Members of high-risk groups/families who want to pursue carrier testing for single gene disorders or chromosome abnormalities (e.g., Duchenne muscular dystrophy, hemophilia, sickle cell anemia, chromosome translocation carrier).
- Questions about genetic diseases or birth defects in immediate or extended family members.
Changes in the normal patterns of sexual development or growth during the teen years should prompt a genetics referral.
The option of carrier testing should be offered to individuals belonging to high-risk families such as the children of an adult diagnosed with Huntington disease. In familial breast, ovarian, or colon cancer, individuals at risk should be identified and counseled.
Individuals diagnosed with an adult onset genetic condition should be advised to discuss the genetics of their condition and the risk to other family members with a clinical geneticist.
The Saad Specialist Hospital Clinical Genetics Service benefits from on-site genetic laboratory services including cytogenetics, metabolic genetics, and molecular genetics laboratories. At Saad Specialist Hospital we offer a cytogenetics and molecular cytogenetics service, newborn screening for common metabolic diseases and molecular analysis for certain disorders.
For couples that are carriers of a known gene mutation, it is now possible to offer pre-implantation genetic diagnosis (PGD), in conjunction with IVF, at Saad Specialist Hospital. This service will benefit many parents of children with genetic diseases.