Why it pays to know your family’s medical history
When you visit a doctor, you usually are asked questions about your extended family’s health. What conditions, if any, do your parents suffer from? Did your grandparents have chronic illnesses?
The answers can be extremely helpful in safeguarding your own health – and that of your family members.
Most people have a family health history of at least one chronic disease, such as cancer, heart disease, or diabetes.
My maternal grandmother suffered from macular degeneration, which causes retinal damage and vision loss, so that means I need to be mindful of this. My paternal grandmother suffered from high blood pressure – so I monitor my own.
I cannot change my genetic make-up, but knowing these two facts about two women whose DNA I share is important.
Often, good lifestyle choices can reduce your vulnerability to the diseases other family members have – and often not just because you share a genetic map; you may share lifestyle choices and habits, and even environment.
Regular screening for the same illnesses they have can be a powerful adjunct to this – for example, blood sugar testing if there’s a susceptibility to diabetes, or mammograms to screen for breast cancer.
A family history can provide information about the risk of rarer conditions caused by variants (mutations) in a single gene, such as cystic fibrosis and sickle cell disease.
“It provides important information about the pattern of transmission of a heritable disease and the risk of having that condition,” says Dr Ivan Chow, a Hong Kong-based specialist in family medicine experienced in chronic disease management.
“Family history can be used as a diagnostic tool and help guide decisions about genetic testing for the patient and at-risk family members. In addition, a family history can even help to exclude genetic diseases.”
There are more than 6,000 known genetic disorders, and around one in 50 people are affected by a known single-gene disorder, and one in 263 by a chromosomal disorder.
Arthur Bozikas, who was born with thalassaemia in the 1960s when screening and treatment were far more rudimentary than they are today, published Iron Boy, a book about living with the condition. It describes a life of “over 8,600 needle sticks, 700 blood transfusions, and 2,200 blood packs”.
He was diagnosed when he was one year old, had his spleen removed by the time he was four years old and, at 20, never imagined living into old age. At 21 though, a new treatment was developed. Bozikas is 60 today.
Chow says that the diagnosis – and treatment or management of heritable disorders – can begin much earlier than it did in Bozikas’ case now, as a result of newborn screening. All babies born in public hospitals in Hong Kong are tested for congenital hypothyroidism and G6PD deficiency, using their umbilical cord blood.
Genetic testing – or premarital screening – is also widely available. This helps couples learn if they carry a gene for genetic diseases and is typically offered to those with a family history of a genetic disorder – which is why it’s important to know your own history – and to people in ethnic groups with an increased risk of specific genetic conditions.
Thalassaemia – Bozikas’ diagnosis – for example, affects people of Mediterranean, Asian or African descent most often. Bozikas is of Greek descent. If both parents are tested, the test can provide information about a couple’s risk of having a child with a genetic condition. Today, to assess the risk of having a baby with thalassaemia, Chow says, parents’ haemoglobin patterns can be assessed before conception.
Genetic testing is not routinely done, Chow says, but a doctor may advise a person to have it if they have a family history of a genetic disorder.
Chow says that people in Hong Kong generally are not aware of heritable diseases simply because many are not that common – for example, congenital hypothyroidism occurs in one in 2,000 to one in 4,000 newborns.
G6PD deficiency is much more common and is believed to affect more than 400 million people worldwide – it affects about 10 to 14 out of every 100 African-American men, for example – though most people remain asymptomatic.
Genetic disorders vary widely in the ratio of people affected: familial hypercholesterolaemia is thought to present in about one in 300 people, cystic fibrosis in about one in 3,000; Wilson’s disease affects one in 30,000. Thalassaemia presents in 5 per cent of the global population.
None of these rarer genetic disorders is present in my family. So for now, I’ll keep up those eye tests and keep off the salt.