Monday, December 2, 2013 C11
HEALTH Beware the risk of sodium in drugs Lifelong drug therapy and monitoring are key to coping with Marfan syndrome, an incurable genetic disorder which causes defective connective tissues, says Sunory Dutt
Illustration: Henry Wong
s a teenager, Ar Tim had an operation to fix a recurring condition called pneumothorax, or collapsed lungs. She has also had surgery for scoliosis. Today, the 35-year-old is subjected to regular cardiovascular tests, as well as electrocardiograms, lung function tests, echocardiograms, regular follow-ups and X-rays of her spine, and occasional CT scans. All this is because Ar Tim has Marfan syndrome. It’s a genetic disorder that causes defective connective tissues which hinder the body’s normal functioning. The incidence of Marfan syndrome in Hong Kong among adults and children is one in 5,000, according to paediatric cardiologist Dr Dora Wong May-ling from the Hong Kong College of Cardiology. Over the years, she has seen an increase in referrals for diagnosis and treatment of Marfan syndrome. A network of connective tissues holds the body together, providing a framework for growth and development. Because these connective tissues are found throughout the body, Marfan syndrome can affect many body systems, including the skeleton, eyes, heart and blood vessels, nervous system, skin, and lungs. The syndrome is not specific to any race or ethnic background. It takes a battery of tests to diagnose the syndrome: heart imaging to determine the proper functioning of the aorta, skeletal imaging to check for abnormal curvature of the spine (scoliosis) or a sunken or protruding breastbone, ophthalmic tests to check for lens dislocation, cataracts, detached retina and glaucoma, and genetic testing. Although a person with Marfan syndrome is born with the disorder, it may not be diagnosed until later in life. Research has found that the child of a person with the syndrome has a 50 per cent chance of inheriting the disease. Wong recalls the case of a man with aortic complications resulting from Marfan syndrome whose two daughters were also diagnosed with the syndrome. However, Ar Tim was diagnosed when she was five years old, despite no family history of it. Even so, the disease has not stopped her from living happily. “I am well aware of the major complications that can arise from the syndrome,” she says. “My lung function is weaker than a normal person’s due to my pneumothorax operation.
HOPES I’ve also had surgery for scoliosis. I avoid strenuous or vigorous exercise. The most important thing is regular drug taking. Other than that, there’s no major change in my lifestyle.” Marfan syndrome may present itself in many ways, according to the US National Marfan Foundation website. Some patients are mildly affected and have only a few of these characteristics, while others are severely affected. Others may have features that fit the characteristics of Marfan patients, but may be fine. Olympic swimmer Michael Phelps’ long arms, slender physique and flexibility were thought to be signs that he has the incurable condition. But he says in his autobiography that he is disease-free. More than half those with the
The syndrome’s severity typically progresses over time. There is, as yet, no known cure syndrome experience minimal or pronounced dislocation of one or both lenses of the eye, and retinal detachment. Many of them are also are myopic, and develop early glaucoma or cataracts. Most people with Marfan syndrome also have problems associated with the heart and blood vessels. Because of faulty
Marfan syndrome is featured with many typical hand characteristics. However a combination of two specific hands signs related to a long hand shape (hand signs) and hand motorics (joint hypermobility) is usually enough to identify the disorder. The Steinberg sign This test is used for the clinical evaluation of Marfan patients.
HEALTH BITES ............................................... Jeanette Wang firstname.lastname@example.org Nanoparticles could spell the end for injections Researchers in Boston have engineered a nanoparticle that can be delivered orally and be absorbed through the digestive tract. The research could allow patients to take a pill instead of having an injection – making it more likely that patients will adhere to their treatment. The researchers, from the Massachusetts Institute of Technology and Brigham and Women’s Hospital, coated nanoparticles with antibodies that unlocked receptors on the surfaces of the cells lining the intestine, allowing the nanoparticles to pass into the bloodstream. The research published in Science Translational Medicine used the particles to deliver insulin in mice, but the researchers say the technique could be used to carry any drug that can be contained in a nanoparticle. The researchers hope to apply the same principles to design nanoparticles that can cross other cellular-level barriers, such as the bloodbrain barrier, which prevents many drugs from reaching the brain.
Fold your thumb into the closed fist. This test is positive if the thumb tip extends from palm of hand.
The Walker-Murdoch sign This test is used for the evaluation of patients with Marfan syndrome. Grip your wrist with your opposite hand. If thumb and fifth finger of the hand overlap with each other, this represents a positive WalkerMurdoch sign. SCMP
connective tissue, the wall of the aorta may be weakened and stretched, a process called aortic dilatation. It increases the risk that the aorta will tear or rupture, causing serious heart problems or sometimes sudden death. Sometimes, defects in heart valves can also cause problems. Valves may leak, creating a heart murmur. Small leaks may not cause any symptoms but shortness of breath, fatigue, and palpitations are possible with larger leaks. The syndrome’s severity typically increases over time. There’s no known cure, except for managing its life-threatening complications with either medication or surgery. Marfan syndrome patients need lifelong monitoring and care. If undetected, the average person’s lifespan rarely extends past 40. But with monitoring and treatment, most people can live into old age. There has been no study on the life expectancy of Marfan syndrome patients in Hong Kong yet, but the median survival age after detection and medication reported by other studies is 70 years. Life expectancy has risen due to treatment advances, early awareness, and intervention. People with Marfan syndrome usually need an annual echocardiogram to monitor the diameter of the aorta, or CT scans and MRIs. If the aorta’s diameter enlarges quickly or reaches a
Oxygen starvation therapy shows promise in treating spinal injuries Exposing patients recovering from spinal cord injuries to short periods of oxygen deprivation may improve their mobility, says a study in Neurology. Participants who were able to walk were exposed to hypoxia, that is they were oxygen deprived. They breathed through a mask for about 40 minutes a day for five days, receiving low levels of oxygen for 90-second periods, followed by 60 seconds of air with ordinary levels of oxygen. The participants were divided into two groups: one group received the treatment and the other a placebo of normally oxygenated air. Two weeks later, the groups were swapped over. After the hypoxia therapy, all participants improved their walking speeds over 10 metres by an average of 3.8 seconds. Link between cholesterol and breast cancer A cholesterol by-product that functions similarly to the hormone oestrogen in fuelling the growth and spread of the most common type of breast cancer has been identified. Science says researchers at the Duke Cancer Institute identified the enzyme 27HC as driving the growth of breast cancers in mice and tumour cells, offering the first explanation for the link between high cholesterol and breast cancer. “The worse the tumours, the more they have of the enzyme,” says lead author Erik Nelson, a post-doctoral research associate at the university. The researchers say there may be a simple way to reduce the risk of breast cancer by keeping cholesterol in check, either with statins or a healthy diet.
dangerous size of about five centimetres, an operation would be necessary to replace that portion of the aorta with a synthetic tube to prevent a lifethreatening rupture. “Cardiovascular disease, mainly aortic root dilatation with complication of aneurysm formation and/or dissection, accounts for the majority of premature death in patients with Marfan syndrome,” says Dr Lun Kin-Shing, honorary clinical associate professor from University of Hong Kong’s department of paediatrics and adolescent medicine. “The early dilation of the aorta can be detected among children,” he says, “through an echocardiograph. But it’s a rare occurrence before their teenage years.” He cites the case of a 15-year-old Marfan patient who was an awardwinning member of his school’s swimming team. He and his parents refused a cardiac operation, despite the discovery of a significant aortic root dilatation in his heart. After two years of explanation, they finally agreed to an operation, which was successful. But not everybody is as lucky. Lun tells of a 12-year-old girl with Marfan syndrome with aortic dissection who successfully had an aortic root replacement. But after two years, she developed chest pains and a dissection was found above the repaired aortic graft. Further replacement of the damaged aorta was performed, but she died suddenly one week after the operation, and a severe new dissection of the whole thoracic aorta was found. In most cases, doctors prescribe medications to lower blood pressure to reduce the strain on the weakened walls of the aorta. Ar Tim, for example, is on a daily medication of a beta blocker to regulate her heart rate and blood pressure. According to Lun, drug therapy using beta blockers is the mainstay of treatment in Marfan syndrome children with aortic root dilatation before surgery. But he says the efficacy of beta blockers to prevent surgery is not yet proven by large scale study. “Treatment using new drugs such as an angiotensin receptor blocker have been proposed, and we are awaiting the results of large randomised trials,” Lun says. Patients need to understand the rationale of life-long drug therapy even after cardiac surgery and should develop good drug compliance. Followup and assessment of the aortic root dimension is important. Lun advises the avoidance of isometric exercise and competitive sports to prevent the small risk of dissection. But other types of recreational exercises are good for cardiovascular health. According to US National Institutes of Health, many studies now under way could lead to a better understanding of Marfan syndrome. email@example.com
................................................ Jeanette Wang firstname.lastname@example.org Could your painkillers be giving you a heart attack? It’s not certain, but it’s possible. The dispersible and effervescent formulations of the common over-the-counter analgesic paracetamol 500mg, for example, can contain a significant amount of sodium – an excess of which has been linked with a greater risk of heart attacks and strokes. If you took the maximum daily dose of eight tablets of paracetemol a day, you’d exceed the recommended total daily allowance of sodium of 2.4 grams by as much as 40 per cent or more. And that’s just from one drug, excluding the sodium you will consume through food. In fact, researchers in Britain have found that patients who took sodium-containing drugs faced a 16 per cent higher risk of a heart problem or stroke, were seven times more likely to develop high blood pressure, and had a 28 per cent higher death rate. “Curiously, unlike foods, pharmaceutical manufacturers are not placed under any restrictions or obligations with regards to sodium content or labelling of these sodiumcontaining formulations,” wrote the researchers from the University of Dundee and University of College London in their study report published last week on the British Medical Journal website bmj.com. They said the public “should be warned about the potential dangers of high sodium intake from prescribed medicines”, and that sodium-containing formulations “should be prescribed with caution only if the perceived benefits outweigh the risks”. They also called for the sodium content of medicines to be clearly labelled in same way foods are labelled. In Hong Kong, as in Britain, “there are no specific labelling requirements for sodium content in registered pharmaceutical products”, said the Health Department. Asked about the possibility of making sodium labelling mandatory for pharmaceutical products in Hong Kong, the department replied: “The [department] shall keep in view of the international practice and development, and review the labelling requirements when necessary.” It’s different in the US. Since 2004, drug manufacturers there are required to list sodium content on the label of prescription drugs and also have a warning label to alert people who are on sodium-restricted diets to consult their doctors before using products that contain more than 140 milligrams of sodium as the maximum daily dose. Effervescent, dispersible and soluble versions of painkillers, vitamin supplements or other common medicines contain sodium for various reasons. The element can aid absorption of
the medicine into the body; as sodium bicarbonate it makes tablets fizz; in other compound forms it can help disperse the medicine or dissolve it in water. Many studies have shown that excess salt – also known as sodium chloride – is harmful to heart health. Eating too much salt contributed to 2.3 million deaths from heart attacks, strokes and other heart-related diseases globally in 2010, representing 15 per cent of all deaths due to these causes, according to research presented at an American Heart Association meeting this year. Seventy-five per cent of the world’s population consumes nearly twice the daily recommended amount of sodium. Global sodium intake from commercially prepared food, table salt, salt and soy sauce added during cooking averaged nearly 4,000mg a day in 2010. The World Health Organisation recommends limiting sodium to less than 2,000mg a day. While the BMJ study researchers acknowledge that
Many studies have shown that excess salt is harmful to heart health
Effervescent painkillers contain a high dosage of salt. there is still some controversy regarding the link between dietary sodium and cardiovascular events, they say their findings “are potentially of public health importance”. In the study, 1.2 million British patients – taking either sodium-containing or nonsodium versions of the same drugs – were tracked for an average of just over seven years. During this time, more than 61,000 cardiovascular events occurred. “Prescription of these sodium-containing formulations should be done with caution, and patients prescribed them should be closely monitored for the emergence of hypertension,” said the researchers.