Geneticists will tell you almost all diseases have a genetic component. Most result from mutations in multiple genes, combined with certain environmental factors. Some conditions – like Down's syndrome – are the result of too many or too few genes. Others are caused by a mistake in a single gene.
Genetics in a nutshell
Genetics are very complicated, but it helps to have a basic understanding of how your genes, chromosomes and DNA are configured.
School biology should have taught you that your body comprises millions and millions of cells, each with a centre, or nucleus, in which your chromosomes are housed. Each chromosome is made up of tightly coiled strands of DNA (deoxyribonucleic acid), which is your body's "blueprint".
Genes are segments of DNA that determine specific traits, such as your nose or chin shape. And you have about 30 000 genes that make you the unique person you are. A gene mutation is a tiny change to your DNA.
These mutations are either inherited, or they can be acquired during your lifetime as your cells age, or are exposed to certain chemicals. These changes to your genes are what result in genetic disorders.
Genes may be classified as dominant or recessive. Dominant genes express their trait even if there's only one copy of that gene in the pair. Recessive genes won't show their trait if there's a dominant gene present – which is why some of your father's traits are more prominent in your make-up, while your brother or sister might take more after your mother.
Your health inheritance
There's a definite genetic component to ailments like heart disease, high blood pressure, migraine and diabetes – all of these, as well as others listed below, tend to run in families.
This doesn't mean that if your father has high blood pressure, you're definitely going to develop it too, for example. Rather, what it means is that you have one of the risk factors for the disease, so you need to be particularly vigilant in that area of your health.
However, you also shouldn't assume that because your parents don't have high blood pressure, for example, you can't get it. Your risk is simply lower than that of a person who has one or both parents with high blood pressure.
Lifestyle component is another important factor in these common disorders which run in families – so you can control your symptoms by eating a healthy, balanced diet, not smoking, exercising regularly and controlling your weight and stress levels.
Allergies
Cape Town-based Dr Harris Steinman, one of South Africa's foremost allergy experts, says allergy definitely has a hereditary aspect. "If neither of your parents has any allergies, you have a 10% chance of being allergic," he explains. "If one parent's allergic, your risk goes up to 25%; if both parents are allergic, it goes up to 50%. If both parents have the same allergy, you have a 75% chance of suffering from allergies."
He adds that certain intolerances tend to run in families too, such as Coeliac disease (an intolerance to wheat), as well as lactose intolerance and even alcohol intolerance.
"Coeliac disease tends to affect mainly white people, but in South Africa you can't exclude other races, because a lot of 'interbreeding' has taken place. Lactose intolerance affects 80-95% of the black population, but only 15% of whites," he notes.
"Lactose-intolerant people lack the enzyme lactase, which helps to digest lactose, the sugar found in milk. It appears we're all born with lactase, but around age five, some children lose the ability to manufacture lactase, to varying degrees.
"Many intolerances have what we call a 'dose effect' – in other words, you might be able to tolerate a glass of milk a day, but two glasses make you ill."
What you can do about it: Allergies tend to be managed, rather than cured, as often the only cure is to remove the allergen (the substance causing the allergy) – which isn't always possible. Allergy testing is also often quite inaccurate – you can get different results two days in a row. Work with your GP and a dietician if you suspect you're allergic to something.
Asthma
Because allergies are often hereditary, so is asthma.
"Children who have parents with asthma and other allergic conditions are definitely at a higher risk of getting asthma," says Johannesburg pulmonologist Dr Günther Schleicher. Asthma's caused when the tiny tubes within your lungs became inflamed and swell, making breathing very difficult.
"Asthma's under-diagnosed and under-treated in South Africa, though it's a very serious disease," stresses Dr Schleicher. "In fact, 5% of asthma attacks are potentially fatal. It also decreases your quality of life through a constant cough and/or continual shortness of breath. And if it's not well treated, your airways may be remodelled, making those little tubes in your lungs permanently narrower. Then what you get is a disease similar to the chronic bronchitis caused by smoking – even if you've never smoked."
What you can do about it: Talk to your GP about any symptoms you think might indicate you've inherited asthma from your parents and then get tested, if necessary. If the diagnosis is positive, ensure you follow the treatment to the letter.
Cancer
Martha Molete, head of communication and advocacy at the Cancer Association of SA (CANSA), says it's not yet known exactly what causes cells to go out of control and become cancerous, but research is now focusing on several areas of possibility.
"Some types of cancer occur in excess in certain families, so researchers are looking for clues in the genes of members of those families. So far, only one form of cancer – retinoblastoma, an extremely rare eye cancer – is considered hereditary (in 40% of cases) and both eyes are usually affected.
"However, it's well known that a specific type of cancer often manifests in a particular family," she continues. "Such persons are usually affected at an early age. Cancers such as breast cancer, colon cancer and melanoma (nevocarcinoma) follow this pattern."
Cancers which tend to run in families and which affect women, in particular, include:
Skin cancer:
Certain families have large, flat, multi-coloured moles. This condition is hereditary and should be monitored carefully by consulting a dermatologist at least annually, or immediately if moles change.
Breast cancer:
If a woman's mother, sister or another member of her immediate family had cancer, especially at a very early age, and if it occurred in both breasts, the chances of her contracting breast cancer are much greater.
CANSA recommends all women conduct regular self-examination of their breasts every month after their period and during a bath or shower. CANSA also recommends annual mammograms from the age of 40, unless breast cancer is in the family – in which case it's important to consult your doctor on when to start mammograms.
Colo-rectal cancer:
Familial poloposis coli (finger-like growths in the large intestine), which are hereditary, may cause cancer in people aged 20-30 years. It's vital that anyone with a familial history of this disease undergoes a colonoscopy on a regular basis, especially if the family tendency is to contract the disease at a young age.
Cardiovascular disease
Having hypertension (high blood pressure) and high cholesterol levels puts you at risk of suffering from a heart attack or stroke, and shouldn't be taken lightly. Hilary Woodley, a dietician with the SA Heart Foundation, says one in four South Africans aged between 15-64 suffers from hypertension, and it's particularly prevalent in the black population.
No-one knows what causes hypertension, but it's dangerous because you can have it for years without showing any symptoms. Prolonged, uncontrolled hypertension can put you at risk of serious health problems like a stroke, as well as damage to many of your body's other vital organs. The higher your blood pressure, or the longer it remains uncontrolled, the greater the damage.
High cholesterol levels mean you have excessive amounts of dangerous blood fats circulating in your veins and arteries. These fats are then deposited on the walls of these blood vessels and, over time, become constricted – resulting in serious complications. You could suffer a heart attack, or you could even lose a leg if the blood supply to your leg becomes blocked.
What you can do about it: Hilary advises controlling your weight. "Losing just 5-10% of your body weight can decrease your cholesterol and blood pressure levels," she points out. She also advises increasing your activity levels, reducing your salt intake and steering clear of fast foods as far as possible, since these are loaded with dangerous fats and salt.
Diabetes
Diabetes mellitus is a group of diseases that affect the way your body uses glucose, a sugar which is your body's main source of fuel. If you have diabetes, you're unable to
process sugar correctly, which means excessive amounts of it are in your bloodstream. That excess causes damage to various parts of your body.
There are two types of diabetes: Type 1 and Type 2.
Type 1 is when your pancreas produces little or no insulin, a hormone which helps your body process sugar. Type 2 is far more common and occurs when your body's resistant to the effects of insulin, or when your pancreas doesn't produce quite enough insulin.
While Type 2 tends to be primarily a lifestyle-related disease, it has a hereditary component, as does Type 1 diabetes. Your chance of developing either type increases if you have a parent or a sibling with the disease.
What you can do about it: Get tested, particularly if you're overweight or have any symptoms such as excessive thirst and/or urination, blurred vision or unexplained weight loss. Then learn to manage the condition: uncontrolled diabetes can result in amputation of toes, feet or even legs, blindness and other frightening symptoms. If you manage diabetes correctly, however, you can stave off many of these consequences.
Migraine
Johannesburg-based neurologist, Professor Vivian Fritz, says there's a familial component to migraines, but only one form is directly hereditary: hemiplegic migraines,
where you experience paralysis on one side of your body.
"The most important factor in migraine treatment is the diagnosis," she adds. "You need to know for sure that you're suffering from a migraine – not just a severe headache. Get a proper diagnosis, as migraines have very specific symptoms, including sensitivity to light, nausea and visual disturbances before the onset of the attack."
What you can do about it: Get a proper diagnosis – from a neurologist, if necessary – and carry your treatment with you, as a migraine can be severely debilitating if not attended to. Also, remember that the best cure for a migraine is sleep, but you need to get rid of the other symptoms first.
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