Episodic ataxia type 1

General Information (adopted from Orphanet):

Synonyms, Signs: CONTINUOUS MUSCLE FIBER ACTIVITY, HEREDITARY, INCLUDED
MYOKYMIA WITH PERIODIC ATAXIA MYOKYMIA 1, INCLUDED
ATAXIA, EPISODIC, WITH MYOKYMIA
MYOKYMIA 1 WITH OR WITHOUT HYPOMAGNESEMIA, INCLUDED
PAROXYSMAL ATAXIA WITH NEUROMYOTONIA, HEREDITARY
ISAACS-MERTENS SYNDROME, INCLUDED
EA1
AEM
EAM
AEMK
episodic ataxia with myokymia
Number of Symptoms 27
OrphanetNr: 37612
OMIM Id: 160120
ICD-10: G11.8
UMLs: C1719788
MeSH:
MedDRA:
Snomed: 421182009

Prevalence, inheritance and age of onset:

Prevalence: No data available.
Inheritance: Autosomal dominant
[Orphanet]
Age of onset: Juvenile onset
[Omim]

Disease classification (adopted from Orphanet):

Parent Diseases: Hereditary episodic ataxia
 -Rare genetic disease
 -Rare neurologic disease

Symptom Information: Sort by abundance 

1
(HPO:0000622) Blurred vision 14 / 7739
2
(HPO:0002321) Vertigo 58 / 7739
3
(HPO:0001260) Dysarthria 329 / 7739
4
(HPO:0001337) Tremor 200 / 7739
5
(HPO:0002315) Headache 175 / 7739
6
(HPO:0002131) Episodic ataxia 16 / 7739
7
(HPO:0002064) Spastic gait 46 / 7739
8
(HPO:0001350) Slurred speech 16 / 7739
9
(HPO:0002411) Myokymia 10 / 7739
10
(HPO:0003487) Babinski sign 179 / 7739
11
(HPO:0001347) Hyperreflexia 363 / 7739
12
(HPO:0001155) Abnormality of the hand 54 / 7739
13
(HPO:0003236) Elevated serum creatine phosphokinase 214 / 7739
14
(HPO:0000006) Autosomal dominant inheritance 2518 / 7739
15
(OMIM) Jerking movements of face and limbs 2 / 7739
16
(OMIM) Myokymia, interictal 2 / 7739
17
(HPO:0003621) Juvenile onset 105 / 7739
18
(OMIM) [DEL]Increased serum creatine kinase during episodes 3 / 7739
19
(OMIM) EMG shows polyphasic continuous motor unit discharges 2 / 7739
20
(HPO:0003828) Variable expressivity 130 / 7739
21
(OMIM) Blurred vision, episodic 3 / 7739
22
(OMIM) Muscle biopsy shows enlargement of type I muscle fibers, consistent with denervation 2 / 7739
23
(OMIM) Leg stiffness 2 / 7739
24
(OMIM) Calf muscle enlargement 2 / 7739
25
(OMIM) Hand posture resembling carpopedal spasm, episodic 2 / 7739
26
(OMIM) Incoordination of the hands 2 / 7739
27
(OMIM) Episodic vertigo 4 / 7739

Associated genes:

ClinVar (via SNiPA)

Gene symbol Variation Clinical significance Reference

Additional Information:

Description: (OMIM) Episodic ataxia is a neurologic condition characterized by spells of incoordination and imbalance, often associated with progressive ataxia (Jen et al., 2007).

- Genetic Heterogeneity of Episodic Ataxia

Episodic ataxia is a genetically heterogeneous ...

Clinical Description OMIM Van Dyke et al. (1975) described a kindred in which 11 persons in 3 consecutive generations had continuous muscle movement (myokymia) and periodic ataxia. Only 2 of the 11 affected were male and no male-to-male transmission was noted. ...
Molecular genetics OMIM Browne et al. (1994) demonstrated mutations in the KCNA1 gene in 4 families with AEMK (176260.0001-176260.0004). A different missense point mutation was present in heterozygous state in each. All affected individuals are heterozygous.

In 2 families ...

Diagnosis GeneReviews Episodic ataxia type 1 (EA1), a neurologic disease resulting from alterations in the voltage-gated potassium channel (Kv1.1), is suspected in individuals with the following clinical findings:...
Clinical Description GeneReviews Episodic ataxia type 1 (EA1), first described in 1975 by Van Dyke et al, is a potassium channelopathy characterized by constant myokymia and dramatic episodes of spastic contractions of the skeletal muscles of the head, arms, and legs with loss of both motor coordination and balance. During attacks some individuals may experience vertigo, blurred vision, diplopia, nausea, headache, diaphoresis, clumsiness, stiffening of the body, dysarthric speech, and difficulty in breathing [Van Dyke et al1975]. ...
Genotype-Phenotype Correlations GeneReviews Due to significant interfamilial and intrafamilial phenotypic variability, reliable genotype-phenotype correlations have been extremely difficult to establish. Indeed, differences in severity and frequency of EA1 attacks have been reported even in monozygotic twins [Graves et al 2010]. ...
Differential Diagnosis GeneReviews Table 2. Episodic Ataxia: OMIM Phenotypic Series...
Management GeneReviews To establish the extent of disease in an individual diagnosed with episodic ataxia type 1, the following evaluations are recommended:...
Molecular genetics GeneReviews Information in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED....