Infantile convulsions and paroxysmal choreoathetosis, familial

Alternate names

ICCA; Convulsions, infantile, with paroxysmal choreoathetosis, familial; ICCA syndrome

Definition

Infantile Convulsions and paroxysmal ChoreoAthetosis (ICCA) syndrome is a neurological condition characterized by the occurrence of seizures during the first year of life (Benign familial infantile epilepsy ) and choreoathetotic dyskinetic attacks during childhood or adolescence.

Epidemiology

This disorder is rare but the exact prevalence is unknown.

Cause

• The genetic loci of ICCA syndrome have been described on chromosomes 16p11.2-q12.1, 16q13-q22.1 and 3q29-29.
• Mutations in the Proline-rich transmembrane protein 2 (PRRT2) gene, located on 16p11.2, have recently been found in families affected by ICCA syndrome. This gene encodes a membrane protein that interacts with the presynaptic protein SNAP-25 but the mechanism leading to the disease remains unknown.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

ICCA syndrome can present as sporadic or familial; in the latter case, it is transmitted as an autosomal dominant trait that can be variably expressed within the same family.

Signs and symptoms

• Benign familial infantile epilepsy begins at 3 to 12 months of age with a family history of the same type of seizures.
• Seizures are afebrile, partial or sometimes generalized, and normally disappear after the first year of life.
• During childhood or adolescence, affected individuals present with paroxysmal kinesigenic dyskinesia with frequent and recurrent episodic choreathetotic or dystonic movements that last less than 1 minute.
• The attacks are triggered by the initiation of voluntary movements or startle.
• The association with other paroxysmal disorders such as migraine, with or without aura, hemiplegic migraine, episodic ataxia and tics has also been described.
• Psychomotor development is normal.

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

• Normal interictal EEG

30%-79% of people have these symptoms

• Athetosis(Involuntary writhing movements in fingers, hands, toes, and feet)
• Choreoathetosis
• Dystonia
• Focal impaired awareness seizure
• Paroxysmal dyskinesia

5%-29% of people have these symptoms

• Complex febrile seizure(Experiential epileptic aura)

Diagnosis

• The diagnosis is mainly clinical, based on the appearance of infantile convulsions with benign evolution followed by kinesigenic dyskinesia attacks later on.
• Genetic testing confirms the diagnosis.

Treatment

Antiepileptic drugs, mainly phenytoin or carbamazepine, are effective in controlling seizures and dyskinesia during the active phase of the disorder.

Prognosis

ICCA has a good outcome. Without treatment, dyskinetic attacks tend to disappear during adulthood.

NIH genetic and rare disease info

• NIH info on Infantile convulsions and paroxysmal choreoathetosis, familial

Infantile convulsions and paroxysmal choreoathetosis, familial is a rare disease.

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