ADCY5-related dyskinesia

Alternate names

Dyskinesia, familial, with facial myokymia; FDFM; Familial dyskinesia and facial myokymia

Definition

ADCY5-related dyskinesia is a movement disorder that is characterized by several different types of involuntary movements.

Epidemiology

At least 400 people have been diagnosed with ADCY5-related dyskinesia, but its prevalence is unknown. The disorder is thought to be underdiagnosed because its features can resemble those of other conditions such as cerebral palsy or epilepsy.

Cause

• ADCY5-related dyskinesia is caused by mutations in the ADCY5 gene.
• This gene provides instructions for making an enzyme called adenylate cyclase 5.
• This enzyme helps convert a molecule called adenosine triphosphate (ATP) to another molecule called cyclic adenosine monophosphate (cAMP).
• ATP is a molecule that supplies energy for cells' activities, including muscle contraction, and cAMP is involved in signaling for many cellular functions.

Gene mutations

• Some ADCY5 gene mutations that cause ADCY5-related dyskinesia are thought to increase adenylate cyclase 5 enzyme activity and the level of cAMP within cells.
• Others prevent production of adenylate cyclase 5.
• It is unclear how either type of mutation leads to the abnormal movements that occur in this disorder.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

• This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.
• In some cases, an affected person inherits the mutation from one affected parent.
• Other cases result from new mutations in the gene and occur in people with no history of the disorder in their family.

Signs and symptoms

• Affected people generally develop sudden jerks, twitches, tremors, muscle tensing, and/or writhing movements between infancy and late adolescence.
• These abnormal movements are often continuous during waking hours and may persist during sleep, resulting in disrupted sleep cycles.
• The arms, legs, neck and face are most commonly involved.
• Hypotonia and delayed motor milestones (i.e. crawling, walking) may also be present in more severely affected infants.

Clinical presentation

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed.

80%-99% of people have these symptoms

• Facial myokymia(Involuntary facial quivering)
• Orofacial dyskinesia

30%-79% of people have these symptoms

• Chorea
• Difficulty walking(Difficulty in walking)
• Dysarthria(Difficulty articulating speech)
• Dystonia
• Limb hypertonia(Increased muscle tone of arm or leg)
• Muscular hypotonia of the trunk(Low muscle tone in trunk)
• Myoclonus
• Resting tremor(Tremor at rest)

5%-29% of people have these symptoms

• Congestive heart failure(Cardiac failure)
• Delayed gross motor development(Delayed motor skills)
• Dilated cardiomyopathy(Stretched and thinned heart muscle)
• Hyperreflexia(Increased reflexes)
• Motor delay

Diagnosis

The diagnosis of of this condition is done in a proband with a hyperkinetic movement disorder (in the absence of structural brain abnormalities) and a heterozygous pathogenic variant of ADCY5 identified by molecular genetic testing.<ref>Hisama FM, Friedman J, Raskind WH, et al. ADCY5 Dyskinesia. 2014 Dec 18 [Updated 2020 Jul 30]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2021. Available from: https://www.ncbi.nlm.nih.gov/books/NBK263441/</ref>[1].

Treatment

Treatment is based on the signs and symptoms present in each person and may include medications, physical therapy, and occupational therapy.

References

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NIH genetic and rare disease info

• NIH info on ADCY5-related dyskinesia

ADCY5-related dyskinesia is a rare disease.

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