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Congenital Mirror Movements Disorder

Clinical Characteristics

Congenital mirror movement disorder is usually characterized by the involuntary movements of one side of the body that follow the movements of voluntary movements on the opposite side of the body. Patients with congenital mirror movements disorder tend to be diagnosed at a young age, since the disorder tends to develop during infancy or early childhood and persist throughout life. The severity of the symptoms can vary from person to person, even between family members. Additionally, the mirror movements are not associated with the onset of any subsequent intellectual manifestations. Furthermore, the movements on the involuntary side tend to be less noticeable than the movements on the voluntary side.

Frequency

Considered to be a rare disorder since less than 1 in out of a million tend to have the disorder. Although this frequency may be higher, since many with a mild condition never get diagnosed.

Genetic Changes

Over 35% of the cases of the disorder are caused by mutations in the DCC or RAD51 genes. The other 65% of cases are likely due to mutations in other genes that have not yet been identified.

Mutation in the DCC Gene

Since mutations in the DCC genes cause impairment, or in some cases, missing, nectrin-1 receptor protein, the dysfunctional nectrin-1 protein impairs the development of the nervous system by hindering the growth of axons during the developmental stage. Subsequently, the movement signals from each hemisphere of the brain is sent to both sides of the body.

Mutation in the RAD51 Gene

The RAD51 gene is thought to make a protein that aids in the development of the nervous system. However, the specifics of the shortage of the RAD51 protein is unclear in how it hinders the development of the nervous system.

Inheritance

The disorder is mostly inherited in an autosomal dominant pattern. In most cases, the person with the disorder has at least one parent with the altered gene. However, some people show reduced penetrance, a situation in which someone with the altered gene never shows the symptoms of the disorder.

Prenatal Testing

If there is an existing biological family member with a mutated RAD51 or DCC gene, pregnancies with increased risk do have the option for genetic testing for the variant. However, differences in perspectives of early genetic testing are prevalent within medical professionals, especially if the purpose of the prenatal testing is for termination and not early diagnosis.

Diagnosis

The physician will ask the patient to do voluntary fine motor movements with each hand, but observe both hands to see if mirroring occurs in the involuntary hand. The involuntary hand will at first appear to be relaxed, but then try to replicate the timing and movement of the voluntary hand during diagnosis. These movements tend to occur predominately in the fingers of the hands, and distal movements tend to mirror more strongly than proximal movements.

Treatment

Preimplantation Genetic Diagnosis

Preimplantation genetic diagnosis may be an option for those whose family has the gene variants identified.

Education Adaptation

Educational facilities should adapt environment to accommodate children with the disorder. Some adaptations include extra time during exams and limited use of handwriting exercises.