Paramyotonia congenita, also called Eulenberg disease, is a rare genetic disorder that affects the muscles used for movement (skeletal muscles). Symptoms of the disorder include long periods of muscle tensing (myotonia) that usually occurs after exercise or exposure to cold. The myotonia becomes worse with repeated movements, unlike other forms of myotonia. Paramyotonia congenita affects the muscles in the face, neck, arms, and hands and typically presents in infancy or early childhood. Fortunately, the symptoms of this disease do not usually become worse with time (not progressive).
Paramyotonia congenita is caused by a change (mutation) in the SCN4A gene and is inherited in an autosomal dominant way, which means a mutation in one of the two copies of the gene a person has is enough to cause the condition. The SCN4A gene acts as an instruction for the body to make sodium ion channels in muscle cells. These channels help the muscles tense (contract) and relax. A mutation in the SCN4A gene leads to abnormal channels, which is the underlying cause of the myotonia. Paramyotonia congenita is suspected in an infant or a child who has myotonia that happens after exercise or exposure to cold temperatures. A doctor may have to take and examine a small piece of muscle (biopsy) to look for clues of the condition and genetic testing is used to confirm the diagnosis. There is no cure for this disease and treatment usually includes avoiding activities that lead to symptoms. If your child has been diagnosed with paramyotonia congenita, talk to their doctor about all treatment options. Support groups can connect you with others affected by this condition.