Genetics in Primary Care
"...Many features of general practice are particularly relevant to genetics. For instance, general practitioners and their teams are skilled in counselling, screening and health promotion and have a special understanding of the impacts of health and disease on patients and families. Primary care also offers the opportunity for staged counselling - the giving and reinforcing of information over a number of consultations. The RCGP argued that general practitioners should not be expected to have extensive genetics knowledge but that it was important that they be able to recognise those with genetic conditions, referring appropriately and reassuring patients with concerns about genetic disease, where guidelines suggest their family history places them at population risk only
Highlighting the knowledge, skills and attitudes about genetics during training is therefore likely to be of value to GPs providing support and management to patients and families with, or at risk of, genetic conditions, and to prepare for future clinical advances. This includes considering the family history in, for example, cancer, cardiovascular disease and diabetes; considering genetic aspects of antenatal and newborn screening; and ethical and social implications of genetic testing. Although regional genetic services continue to work in partnership with general practice over the care of families with Mendelian and chromosomal disorders, as genetics increasingly shifts to encompass common disorders, general practitioners are likely to deal with progressively more genetic information...(1)"
Some basic definitions used in genetics:
Common and/or important genetic conditions
With reference to common chromosome anomalies:
- Down Syndrome
- what is the chromosomal abnormality accounting for 95% of Downs syndrome?
- other cases of Downs syndrome may be due to a translocation. What is a translocation?
- what is the risk of Downs syndrome in a child born to a mother who is 40 years old?
- duodenal atresia and Hirschsprung's disease are examples of gastrointestinal abnormalities associated with Downs syndrome. What cardiac abnormalities are associated with Downs syndrome?
- Turner syndrome
- what is the genetic abnormality that causes Turner's syndrome?
- review of the clinical features of Turner's syndrome
- what is a Turner's syndrome mosaic?
- Klinefelter syndrome
- most common cause of male hypogonadism with an incidence of approximately 1 in 1000 male births. Individuals have an extra X chromosome. Usually, the karyotype is 47, XXY
- what are the clinical features of Klinefelter's syndrome?
With reference to single gene disorders:
- autosomal dominant disorders include:
- adult polycystic kidney disease
- what is the genetic abnormality?
- what extrarenal manifestations are associated with this disorder?
- Neurofibromatosis is a term used to describe two different diseases with some overlapping features. The types of neurofibromatosis are:
- von Recklinhausen's disease, peripheral or type I neurofibromatosis
- bilateral acoustic neurofibromatosis, central or type II neurofibromatosis
- what is the genetic disorder associated with type I neurofibromatosis?
- what dermatological features are associated with type I neurofibromatosis?
- Huntington disease
- what is the genetic disorder associated with Huntingdon's disease?
- a review of the clinical features and course of Huntingdon's disease
- familial hypercholesterolemia (FH)
- what features are suggestive of probable FH?
- what is the receptor abnormality associated with FH?
With reference to Autosomal Recessive disorders:
- Cystic fibrosis (CF)
- the most common potentially lethal autosomal recessive disorder in Caucasian populations, characterised by chronic suppurative lung disease and chronic exocrine pancreatic insufficiency. It affects 1 in 2500 infants
- how might an undiagnosed CF present?
- what are the gastrointestinal features of CF?
- Haemoglobinopathies (Sickle cell disease, Thalassaemias)
- chronic haemolytic disorder with intermittent acute crises. The sickle haemoglobin gene shows autosomal recessive inheritance. Patients with sickle cell disease are homozygous for the mutant globin gene which has a substitution of valine for glutamine at the sixth position in the beta-subunit
- what is the epidemiology of sickle cell disease?
- synoposis of features of painful sickle cell crises
- the prevalence of being a carrier for beta-thalassaemia in the UK Pakistani community is approximately 1 in 25 T/F?
- the estimation of the gene frequency for this condition in Northern Europe could be as high as 1 in 4 T/F?
- the bronzed skin that may be associated with haemochromatosis is caused by iron deposition in the subcutaneous tissues T/F?
With reference to X-linked disorders:
- Duchenne's Muscular Dystrophy
- inherited in an X-linked manner although up to 30% of cases represent new mutations. The gene for Duchenne muscular dystrophy (DMD) is the dystrophin locus at Xp21. occurs in approximately 1 in 3500 male births
- can DMD affect females?
- what cardiac abnormalities are associated with DMD?
- Becker's Muscular Dystrophy
- X-linked inherited muscular dystrophy with the disorder occurring at locus Xp21.2. It is a less severe from of muscular dystrophy than Duchenne's muscular dystrophy. Incidence is 1 in 20,000 live births
- GPN reference
- Haemophilia A
- congenital deficiency of factor VIII (VIII:C) coagulant activity. It is an X-linked recessive disorder affecting 1 in 10 000 males
- commonly, first presentation is at about 6 months when the infant starts to crawl T/F?
- Fragile X
- fragile X syndrome increases in severity down the generations of an affected family T/F?
Examples of familial cancers:
- Breast cancer
- BRCA2 is associated with a higher risk of breast cancer development than BRCA1? T/F
- Colon cancer
- the majority of cases of familial polyposis coli are sporadic? T/F
Examples of conditions exhibiting variable inheritance patterns
- an example of such a condition is Alport's syndrome
Useful additional reading:
- Royal College of General Practitioners (April 2006). Curriculum Statement 6 Genetics in Primary Care.