Paramyotonia Congenita: Causes, Symptoms, and Treatment
Medically reviewed by Harsha Moole, MD, Internal Medicine. Last reviewed: October 2, 2026.
What kind of doctor treats Paramyotonia Congenita?
A primary care doctor is often the first person to notice the pattern of symptoms and start the evaluation. The main specialist is a neurologist, a doctor who treats conditions of the nerves and muscles. A direct primary care doctor, who charges a flat monthly fee instead of billing insurance, can be a good home base for this condition.
What it is
Paramyotonia congenita is a rare muscle condition that a person is born with. It causes muscles to stiffen and become hard to relax after they are used. Unlike some other muscle stiffness conditions, the problem gets worse with exercise and with cold. Most people with the condition live full, active lives.
Symptoms
The main symptom is muscle stiffness that does not ease with continued movement. Cold makes the stiffness much worse. Symptoms often appear after swimming in cool water or being outside in winter. The face, hands, and forearms are affected most often. Some people also have periods of weakness that can last hours after the stiffness. Symptoms usually show up in childhood.
Causes and who gets it
The condition is caused by a change in a gene called SCN4A. When the channel does not work right, the muscle has trouble relaxing after it contracts. The condition is passed down in an autosomal dominant pattern, meaning a child only needs to inherit the changed gene from one parent to have it. Men and women are affected equally.
How doctors diagnose it
A doctor will ask about symptoms, especially whether cold or exercise makes the stiffness worse and whether family members have similar problems. One common test is called an EMG, short for electromyography. Genetic testing on a blood sample can confirm the diagnosis by finding the change in the SCN4A gene.
Treatment
There is no cure, but many people manage well with simple steps. Staying warm is the most helpful change, since cold triggers stiffness. Warming up gently before activity and avoiding sudden intense exercise can also help. Some people are given medicines that calm the overactive sodium channels, such as mexiletine.
When to see a doctor
Anyone with muscle stiffness that lasts a long time, gets worse with cold, or runs in the family should talk to a doctor. Medical care is needed right away if someone has trouble breathing, trouble swallowing, or severe weakness. Children with slow-opening eyelids or stiffness after swimming should also be evaluated.
Common questions
Is paramyotonia congenita life threatening?
No. The condition affects how muscles relax, but it does not damage the heart or shorten life. The main limits are stiffness and sometimes weakness after cold or exercise.
Will my children inherit it?
If one parent has the condition, each child has a fifty percent chance of inheriting the changed gene. Genetic testing and genetic counseling can help families understand the details.
Does exercise make it worse?
For many people, yes. Unlike other stiffness conditions, repeated movement in paramyotonia congenita tends to increase stiffness rather than ease it. Gentle warm-ups and avoiding cold during activity usually help.
Can it be cured?
There is no cure, but symptoms often can be managed. Staying warm and, for some people, taking medicine can reduce stiffness. Results vary from person to person.
Sources
- NIH Genetic and Rare Diseases Information Center - Paramyotonia congenita of Von Eulenburg
- MedlinePlus Genetics - Paramyotonia congenita
- Muscular Dystrophy Association - Paramyotonia Congenita
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
