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Periodic Paralysis In Focus Dear Readers Fast Facts This “In Focus” report is the third in a series of MDA’s three-year commitment for all Hypokalemic periodic paralysis MDA comprehensive reports about the latest in periodic paralysis research as of March Hypokalemic PP can begin anywhere from neuromuscular disease research and manage- 2009 is $1,938,367. The Association’s early childhood to the 30s, with periodic ment. allocation for research on hyperkalemic attacks of severe weakness lasting hours This report focuses on the periodic and hypokalemic periodic paralysis to days. The frequency of attacks gener- paralyses, a group of disorders that result from research since 1950 is $8,125,341. ally lessens in the 40s or 50s. Permanent malfunctions in so-called ion channels, micro- MDA’s allocation for the recently weakness may persist between attacks, scopic tunnels that make possible high-speed identified Andersen-Tawil syndrome usually beginning in middle age and pro- movement of electrically charged particles is $515,430 since 2001. MDA is cur- gressing slowly over years. across barriers inside cells and between cells rently funding 11 grants in the periodic The most common underlying cause and their surroundings. paralyses. is any of several genetic mutations in When ion channels fail to open or close The periodic paralyses are gener- a gene on chromosome 1 that carries according to an exquisitely fine-tuned program, ally divided into hyperkalemic periodic instructions for a calcium channel protein episodes of paralysis of the skeletal muscles paralysis, hypokalemic periodic paralysis in skeletal muscle fibers. When this chan- and even temporary irregularities in the heart- and Andersen-Tawil syndrome. The first nel fails to transmit a signal to a calcium beat can occur. two are caused by genetic defects in storage area inside the cell, the muscle Throughout history, and unfortunately high-speed tunnels in skeletal muscle fiber can’t contract. A minority of people down to the present day, people who experi- fibers known as ion channels. The last is have sodium channel mutations, but not ence episodes of paralysis or weakness, inter- due to such defects in both skeletal and the same ones that cause hyperkalemic spersed with periods of normal functioning, cardiac muscle. periodic paralysis. have been met with suspicion by their peers All forms of periodic paralysis affect and even their doctors. Individuals have been both sexes equally and are inherited in Andersen-Tawil syndrome accused of faking their attacks to gain atten- a dominant manner, meaning only one This syndrome usually begins in child- tion or shirk their responsibilities, and parents genetic flaw (mutation) from one parent hood or adolescence and is characterized have been suspected of child abuse when their can cause the disease. by episodes of weakness of the skeletal children displayed these mysterious symptoms. muscles and irregular heartbeat in the Today, molecular biology has pinpointed the Hyperkalemic periodic paralysis cardiac muscle. Occasionally people may precise mechanisms that underlie the periodic Hyperkalemic PP usually begins early develop permanent weakness between paralyses, and drug trials to treat them are in childhood, with episodes of muscle episodes. Heartbeat irregularities can under way. There is much work to be done, but weakness or paralysis lasting from 15 be serious enough to warrant treatment awareness of the diagnosis can provide signifi- minutes to hours or even days. With with medication or electronic devices. cant reassurance and help in managing these time, some people develop permanent Widely spaced eyes, low-set ears and a conditions. mild or moderate weakness that persists small chin also are characteristic of this This special section includes: between bouts of severe weakness. disorder. • “Fast Facts” about periodic paralysis Some patients also experience episodes The underlying cause of Andersen- • An update on state-of-the-art research and of myotonia, the inability to relax mus- Tawil syndrome is any of a number of disease management, with first-person cles completely. genetic mutations in a chromosome 17 stories from families affected by periodic The underlying cause is any of sev- gene for a potassium ion channel present paralysis eral genetic mutations in a gene on chro- in both skeletal and cardiac muscle tissue. • Information about genetic testing mosome 17 that carries instructions for When these channels fail to open, the To learn more about periodic paralysis, visit a sodium channel protein. The sodium exit of potassium from muscle cells after www.mda.org or call your local MDA office at channels in skeletal muscle can’t close they contract is impaired, and the cells (800) 572-1717. properly, permitting an excess of sodium can’t “reset” to receive further contraction ions to enter the muscle fibers. signals. 1 In Focus: Periodic Paralysis ©2009 MDA In Focus: It’s All in the Muscles, Not the Head Individuals and families struggle to manage the periodic paralyses, a group of diseases that’s too often misunderstood by teachers, employers and even health professionals by Margaret Wahl People who know me know I lead an visited the MDA clinic at Yale University added to local extremely active life,” says Linda Feld in New Haven, Conn., where a doctor anesthetics, of Longwood, Fla. “People don’t see me suggested her condition might be peri- also can cause as somebody on a scooter. I’m Linda, odic paralysis but wasn’t sure. problems. If and I do all these things every day, and She tried to work, but soon “it the respiratory they know me for me. I tell people that became more and more difficult to hold muscles are periodic paralysis has become my friend. down a job. The weakness episodes affected, respi- It’s along for the ride, but it’s not going to would come on, and I couldn’t get out of ratory insuf- rule my life.” my desk chair at work. I’d be sitting there ficiency can Feld, now 59 and a hospice volunteer, working and couldn’t get up to go to the result. Linda Feld didn’t get a says her experience with the genetic copy machine. It became impossible to Feld’s father definitive diagnosis until she disease she now knows as hypokalemic hold a job.” became com- was 56 years old. (“low potassium”) periodic paralysis As she aged, the paralysis episodes pletely paralyzed after the anesthesia he goes back to her earliest memories, at ceased, but were replaced by progres- was given for the tracheostomy proce- age 3 or 4. sive and ultimately permanent weakness. dure and succumbed to a respiratory “I would develop a limp [periodical- (The lack of episodes and the permanent arrest a few days later. ly],” she recalls. “We’re talking the early weakness made diagnosis even more Feld finally got a definitive diagnosis 1950s, and not much was known about elusive.) She tried breeding dogs, but the when she was 56 years old, through the periodic paralysis. Even though my father work of maintaining a kennel eventually laboratory of Frank Lehmann-Horn at was disabled, he didn’t have a diagnosis.” proved too taxing. Ulm University in Germany. An orthopedic specialist suspected Feld’s sister, Sally, nine years younger, Lehmann-Horn, who received several her legs were of unequal length and pre- began following a similar pattern. “When MDA grants in the 1990s to study the scribed a lift for her shoe and supportive she reached her teenage years, she periodic paralyses, was originally trained footwear. “It was always very important started with terrible episodes of muscle as an engineer, later becoming a medical to my parents that I wore really sturdy cramping,” Feld recalls. Sally was given doctor. He’s widely regarded as an out- shoes. I wanted to be like the other kids an erroneous diagnosis of limb-girdle standing contributor to the study of ion and wear sneakers,” Feld says. muscular dystrophy. channel physiology, having done more to “I was never good at gym in school. Their father retired at age 55 because describe its behavior in health and dis- There was teasing by fellow classmates. of continued weakness, including weak- ease and to apply his findings to patient I couldn’t run fast. When I reached ness of his respiratory muscles. A bad care than perhaps any other professional. my teen years, I started having terrible chest infection when he was 72 caused Feld says the disease has forced many muscle cramps. There was nothing that his doctor to recommend a tracheostomy, compromises in her life. “I had to learn would alleviate the pain. The muscles a surgical opening in the trachea, through I could not be everything that every- became rock hard. It was not my whole which mucus would be suctioned out. body else was. I couldn’t be the athlete, body, always just a limb. Those cramps The family was unaware at the couldn’t follow the crowd and do what lasted 24 to 48 hours. Then they would time that certain anesthetics, both gas they did. I couldn’t go out and go drink- start to subside, but the weakness took and local, and muscle relaxants called ing with them. Alcohol was a big trigger. weeks to come back from. I missed big “depolarizing” agents, frequently used I wish I had known earlier in life some of segments of school.” during surgery, can cause long-lasting the things that work for people.” Feld finished high school and went on and severe weakness in people with Today, she manages her disease with to college. When she was about 20, she periodic paralysis. Epinephrine, often a medication called eplerenone (Inspra), 2 In Focus: Periodic Paralysis ©2009 MDA which keeps her serum potassium levels negative charge.
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