Answers to questions families often have about caring for their child with myotonic muscular dystrophy

Myotonic muscular dystrophy (MMD) is an inherited muscle condition that causes slowly progressive muscle weakness and wasting and associated symptoms. Children who are born with myotonic muscular dystrophy have the congenital form, and have a more severe form of the condition, often having swallowing and breathing problems at birth. These early life problems often improve significantly over time. Involved muscles are usually in the face, jaw and neck area. Muscle stiffness or "myotonia" is characteristic, especially affecting the hands, though this typically doesn’t happen until the teenage years. Associated problems include:

• cataracts
• heart arrhythmias
• learning problems
• frontal balding
• diabetes

Most MMD is caused by a mutation on chromosome 19 where an unstable area of the chromosome expands from a slight expansion in mildly-affected individuals to a large one in severely-affected children usually with the congenital form. There is another form of MMD, type 2, that is caused by an unstable area on chromosome 3. It is similar, but not the same as MMD type 1.

Myotonic muscular dystrophy is an inherited condition. This condition follows a "dominant" inheritance pattern, which means that on average half of the children of an affected person are themselves affected. Both men and women are equally likely to be affected and to pass on the disorder, but affected women are more likely to have a severely-affected child. If the disease is inherited through the mom, the disorder tends to be more severe in successive generations (i.e., to show “anticipation”).

Symptoms of the congenital (present at birth) form:

• breathing problems
• high arched palate
• difficulty eating
• muscle contractures
• distinctive facial features due to facial muscle weakness
• myotonia which is present in older children and adults is not present in infants, although often it is possible to find myotonia in the infant's mother

• muscle weakness, especially face, neck, hands, giving the face a distinctive appearance
• muscle contractures, especially heel cords
• myotonia
• frontal balding
• diabetes
• heart arrhythmias

MMD is diagnosed with a gene test performed on a blood sample.

Children with the congenital form may have severe difficulties. Individuals with the later-onset form have very slowly-progressive weakness. Due to abnormalities in swallowing muscles, choking may be a problem. Older individuals may have heart arrhythmias and should be periodically monitored by cardiology and should do well with proper preventive care.

If you have suspicions that other children or adults in the family have myotonic dystrophy, they should be examined by a specialist.

If you have 1child with myotonic muscular dystrophy, any future children carry a 50% risk of also having MMD. If the condition is inherited through the mom, a more severe form of MMD, congenital MMD, may occur in those future children.

There is no specific treatment for myotonic muscular dystrophy although specific symptoms such as drooling and fatigue may be treated symptomatically.

Yes, you should certainly tell the school, as it will help them to know that he has a medical condition. Some of his problems may be due to poor speech from his face and jaw muscles being affected, daytime sleepiness, or due to difficulties paying attention. Where the condition has been present from early childhood there can be true learning difficulties and he may need psychological testing to see if this is the case or not. He may be eligible for a statement of special needs which would allow him to have assistance with his schooling. See Myotonic Dystrophy Support Group (MDSG).

Myotonic dystrophy affects both sexes equally and can be passed on by both men and women. It is quite different in that respect from other muscular dystrophies, especially the Duchenne type, which only affects males but is passed on by healthy females. Any child of an affected person has a 50% risk of inheriting the disorder. If a family member is unaffected and shown to be free of it by full testing, it is most unlikely to be passed on by that person.

Yes, even those who are mildly affected by MMD have a higher risk when they receive anesthesia. Your family doctor should be told and any surgeon and anesthesiologist who treats you. Leaflets on detailed precautions are available, as is a warning card to carry (see Myotonic Dystrophy Support Group (MDSG)). If an operation is really necessary, it should be carefully planned and done in a hospital with an intensive care unit, just in case. Most problems happen because doctors (and patients) are not aware of the possibility of a problem. The main problems are because the breathing muscles are weak and sensitive to anesthetics and drugs used after surgery, as well as disturbances of the heart rhythm.

For unclear reasons, children and adults with MMD fatigue very easily. Adults will describe having to take a nap after doing simple household tasks. Although there are several medications that might be helpful for fatigue in older children and adults, including stimulants and modafinil, these are rarely used in young children. Behavioral management should include keeping to set bedtimes, naptimes, wakeup times, and planned rest periods during the day. Energy conservation is also important. The family should be encouraged to use a disability placard/plate for their car to preserve the child's energy.

Children with congenital myotonic muscular dystrophy often have significant facial muscle weakness that may lead to drooling. Drooling can be a social barrier and will often respond to treatment. Your first step should be to consult a feeding specialist for a thorough evaluation of your son's oral abilities. Depending on results, there are several treatment options. The feeding specialist may be able to give your son strategies to alleviate drooling. If that is not successful, a visit to an otolaryngologist may be helpful for the consideration of temporary treatments (botulinum toxin injections) to decrease drooling or longer-lasting surgical treatment.

Most children who are born with the congenital form of MMD inherit it from their mother, although in general myotonic dystrophy can be inherited from a mother or a father. It is one of the most common muscular dystrophies.