Alternating Hemiplegia of Childhood 1; AHC1

What is Alternating Hemiplegia of Childhood 1; AHC1?

Alternating Hemiplegia of Childhood 1; AHC1 is a rare disease. It is also known as AHC Alternating hemiplegia of childhood..

Alternating hemiplegia is thought by some to be related to migraine, but as others point out the clinical picture can be very different. Onset is between one and 20 years. The first attacks might be dystonic rather than hemiplegic (in some the onset is with focal seizures - often atypical twitches) and several attacks might occur each month, lasting from a few minutes to a few days. During attacks, there might be nystagmus, strabismus, vasomotor disturbances, and screaming as if in pain. After several attacks more permanent neurological sequelae might persist, including focal pyramidal or extrapyramidal signs. See under 'Hemiplegia - benign, nocturnal, alternating' - for something similar. Cardiac involvement (faulty cardiac repolarization) might be common (Jaffer et al., 2015).
Most cases are sporadic, although there might be a family history of migraine, but note the paper by Mikati et al., (1992), in which the condition is segregating with a balanced translocation (3:9). Mental retardation was a feature in some. A mother and four sons (all mentally handicapped) were reported by Xaidara et al., (1998), and the same family by Kanavakis et al., (2003) and half-sisters (same mother) by Kramer et al., (2000).
Bassi et al., (2004) described a Greek family with four affected in two generations. Because of the partial overlap with familial hemiplegic migraine, the authors screened ATP1A2 and found a novel heterozygous mutation. Another ATP1A2 mutation was reported by Swoboda et al., (2004), but mutations were not found in the six patients reported by Kors et al., (2004) nor in 23 patients reported by Vuillaumier-Barrot et al., (2011). Mutations in ATP1A3 could be responsible for 74% of cases (Heinzen et al., 2012).
Sasaki et al., (2014) studied 35 Japanese patients and found de novo heterozygous mutations in ATP1A2 in 33. They found that Glu815Lys mutations had the most severe phenotype.
Three patients with novel heterozygous missense mutations in the ATP1A3 gene were described by Marzin et al., (2018). Clinical characteristics included severe developmental delay, seizures and early onset movement disorder. No hemiplegic attacks were observed.
Fusco et al. (2003) described 29 individuals from two unrelated families with familial hemiplegic migraine type 2, associated with ATP1A2 gene haploinsufficiency. Four patients suffered from migraine aura without motor weakness, five had a history of seizures, and two had mild mental retardation.

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* This information is courtesy of the L M D.

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What gene changes cause Alternating Hemiplegia of Childhood 1; AHC1?

The syndrome is inherited in the following inheritance pattern/s:

Autosomal Dominant - In the case of autosomal dominant inheritance, just one parent is the carrier of the gene mutation, and they have a 50% chance of passing it onto each of their children. Syndromes inherited in an autosomal dominant inheritance are caused by just one copy of the gene mutation.


Uncertain - The exact mode of inheritance was unknown at the time this entry was recorded.


Sporadic - In some cases, a genetic syndrome may be the result of a de-novo mutation and the first case in a family. In this case, this is a new gene mutation that occurs during the reproductive process.


In some cases, a genetic syndrome may be the result of a de-novo mutation and the first case in a family. In this case, this is a new gene mutation that occurs during the reproductive process.

OMIM Number - 104290 (please check the OMIM page for updated information)

The syndrome can be caused by mutations in the following gene/s location/s:
ATP1A2 - 1q23.2

What are the main symptoms of Alternating Hemiplegia of Childhood 1; AHC1?

The typical symptoms of the syndrome are:
Mental deterioration, Intellectual disability, Episodic quadriplegia, Episodic hemiplegia, Bilateral tonic-clonic seizure, Headache, Choreoathetosis, Autosomal dominant inheritance, Nystagmus, Dystonia

How does someone get tested for Alternating Hemiplegia of Childhood 1; AHC1?

The initial testing for Alternating Hemiplegia of Childhood 1; AHC1 can begin with facial genetic analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the type of genetic testing needed. A consultation with a genetic counselor and then a geneticist will follow.

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.

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