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When cold paralyzes the body - Living with rare muscle disease

While others enjoy the first ice cream cone in spring, start to sweat in their jackets and discover a little sunburn on their nose in the evening, Matthias* wears gloves. He also meticulously keeps the rest of his body warm. Too warm, healthy people would say. But Matthias is not healthy.

The 33-year-old Berliner suffers from a rare disorder; the so-called Paramyotonia Congenita according to Eulenburg - a hereditary sodium channel disease. Only one person out of 180,000 people in Germany is affected. The disease makes it impossible for him to go through life carefree. At all times, he has to be careful that his body does not cool down. At temperatures of ten degrees or colder his muscles stiffen within a few minutes - sometimes only for a short time, at worst for several hours. His hands in particular cramp up, becoming as solid as concrete. A drug cannot free him from this rigidity. He has to wait until the attack on his muscles passes on its own. It's agonizing, he says.

Cold, exercise or carbohydrates can trigger attacks of paralysis

What is the reason? The disorder belongs to the family of ion channel diseases, which also includes hypokalemic periodic paralysis (HypoPP). HypoPP has many different faces and is always manifested by attacks of paralysis. The trigger may not only be cold - some patients have to be careful of carbohydrates, of sports or too much alcohol. Even one's own fears can literally paralyze them. In the worst case, patients lie paralyzed in bed for hours. About half of them develop muscle atrophy with walking difficulties as they get older. A wheelchair is often unavoidable.

Symptoms since early youth - "Couldn't undo the button on my pants"

For Matthias, the cold is the enemy. "Even as a little boy, I couldn't take my shoes off by myself or undo the button on my pants after soccer games in fresh temperatures," he recalls. The muscles in his hands had become stiff. He could no longer stretch his fingers. Even on his bicycle, he often felt his hands close tightly around the handlebars, seeming to melt into them. To loosen the hand? Hopeless. Matthias had to learn to endure it. Today he is an expert on his own body. He knows what works - and what doesn't. Indoor swimming pools and lakes are a no-no for him, as is going to the stadium in cool temperatures. Matthias was also restricted in his choice of profession. "I had to rule out anything that relied heavily on fine motor skills in the fingers," he says. He could never have become a surgeon, a musician, a craftsman - fortunately, he didn't want to. Matthias is a doctoral student in the natural sciences at a research institute in Berlin. He has to be careful when he has to handle pipettes, tweezers or scissors there. He doesn't ride his bike, but takes the train to protect his hands from the wind and chilling.

Illness is often misjudged - many sufferers are sent to a psychiatrist

Matthias has developed his strategies for coping with the disease. He learned this from his father. He also suffers from the rare disease, which was diagnosed when he was in military service. Matthias' grandmother, uncle and cousin are also affected. There is no cure.

Where do the muscle attacks come from? What happens in the body that causes muscles to cramp up like this? Private lecturer Dr. Karin Jurkat-Rott, a physiologist at the Institute of Applied Physiology at the University of Ulm, discovered the cause.

"The muscles become paralyzed in hypokalemic periodic paralysis due to a drop in the concentration of potassium in the blood," she explains. "When the potassium in the blood returns to normal, the muscle spasms resolve." It's like a haunting that comes and goes, she says. That's why the disorder is often misdiagnosed and patients are often sent to a psychiatrist - even though they need a neurologist.

MRI examinations provide decisive clues

Wie kann man Patient:innen helfen? Was lässt sich tun gegen den Abfall der Kaliumkonzentration im Blut? Karin Jurkat-Rott wollte eine Antwort finden und forschte weiter – gemeinsam mit Professor Dr. Marc-André Weber, Direktor des Instituts für Diagnostische und Interventionelle Radiologie, Kinder- und Neuroradiologie an der Universitätsmedizin Rostock. Sie untersuchten Betroffene mithilfe von Kernspintomographien (MRT) und stellten bei ihnen Natrium- und Wassereinlagerungen fest. Auch Matthias nahm an den Studien teil. Eines seiner Beine wurde dafür mit Hilfe von Eis heruntergekühlt, gleichzeitig musste Matthias seine Beinmuskeln beanspruchen.  „Muskelarbeit und Kälte sind ein maximaler Trigger“, erklärt er. In diesem Zustand fand die MRT-Untersuchung statt. Die Wissenschaftler:innen hatten dadurch den Seitenvergleich: Die Darstellung des nicht heruntergekühlten Beins und des gekühlten Beins. Im gekühlten Bein war die erhöhte Natriumeinlagerung auch bei Matthias zu sehen.

Diuretics help to relieve symptoms

In order to drain the tissue and increase the potassium in the blood, the researchers administered a drug that is actually used to treat heart failure - colloquially known as "diuretic tablets" - to two patients with hypokalemic periodic paralysis as part of an individual healing trial. Both patients suffered severely from their disease, had muscle atrophy and were confined to a wheelchair. The effect of the medication was impressive: both patients no longer suffered from paralysis. Their muscle strength also improved so much that they were able to walk independently again.

In 2010, the two scientists received the Eva Luise Köhler Research Award for Rare Diseases for their new therapeutic approach. But their efforts to help those affected did not end there. The scientists used the award money to further investigate the importance of potassium, sodium and chlorine in muscle diseases. "There are a variety of muscle diseases," explains Professor Marc-André Weber. "We hope to further develop therapeutic options for them as well."

Future task: testing the effect of the drugs even more precisely

To do this, it is necessary to determine the distribution of chloride in the blood and in the muscle cells. This is possible with state-of-the-art magnetic resonance imaging equipment, which was co-financed with money awarded from the Eva Luise and Horst Köhler Foundation for People with Rare Diseases. "This procedure allows us to check the effect of various diuretic drugs after a very short duration of therapy," explains Professor Marc-André Weber.

Fortunately, Matthias has been able to live without the medication so far - but it is an option when he knows that he cannot escape the cold. He himself has come to terms with his illness - and doesn't let it stop him from eating ice cream in the spring. "It can paralyze my tongue a little bit for a minute," he says. "But it will pass."  For people who have been hit harder, he wishes that science keeps moving forward. Professor Marc-André Weber and private lecturer Dr. Karin Jurkat-Rott give their best. 

*Name changed by the editor

Weitere Informationen zum Forschungsvorhaben

Text: Sandra Arens
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