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Epilepsy, progressive myoclonic, 1B(EPM1B)

MedGen UID:
Concept ID:
Disease or Syndrome
Synonyms: PME; Progressive myoclonus epilepsy with ataxia
SNOMED CT: PRICKLE1-related progressive myoclonic epilepsy with ataxia (702326000); Progressive myoclonic epilepsy 1B (702326000); Progressive myoclonus epilepsy with ataxia (702326000)
Gene (location): PRICKLE1 (12q12)
Monarch Initiative: MONDO:0012904
OMIM®: 612437

Disease characteristics

Excerpted from the GeneReview: PRICKLE1-Related Disorders
Individuals with biallelic PRICKLE1-related disorders typically present with progressive myoclonus epilepsy (PME) with ataxia characterized by myoclonic seizures (lightning-like jerks), generalized convulsive seizures, varying degrees of neurologic regression mainly presenting with ataxia, and mild cognitive impairment or normal cognition. Onset of symptoms is between ages five and ten years. Action myoclonus may affect the limbs or bulbar muscles, while spontaneous myoclonus may occasionally involve facial muscles. Dysarthria may also be an early feature of this condition. The main seizure types are myoclonic or tonic-clonic with frequent nocturnal occurrence. Individuals with heterozygous PRICKLE1 pathogenic variants have presented with non-PME seizures (isolated myoclonic seizures, juvenile myoclonic epilepsy), myoclonic epilepsy, developmental delay, intellectual disability, autism spectrum disorder, and/or central nervous system malformations. [from GeneReviews]
Mario Mastrangelo  |  Caterina Caputi  |  Dario Esposito, et. al.   view full author information

Additional description

From MedlinePlus Genetics
PRICKLE1-related progressive myoclonus epilepsy with ataxia is a rare inherited condition characterized by recurrent seizures (epilepsy) and problems with movement. The signs and symptoms of this disorder usually begin between the ages of 5 and 10.

Problems with balance and coordination (ataxia) are usually the first symptoms of PRICKLE1-related progressive myoclonus epilepsy with ataxia. Affected children often have trouble walking. Their gait is unbalanced and wide-based, and they may fall frequently. Later, children with this condition develop episodes of involuntary muscle jerking or twitching (myoclonus), which cause additional problems with movement. Myoclonus can also affect muscles in the face, leading to difficulty swallowing and slurred speech (dysarthria).

Beginning later in childhood, some affected individuals develop tonic-clonic or grand mal seizures. These seizures involve a loss of consciousness, muscle rigidity, and convulsions. They often occur at night (nocturnally) while the person is sleeping.

PRICKLE1-related progressive myoclonus epilepsy with ataxia does not seem to affect intellectual ability. Although a few affected individuals have died in childhood, many have lived into adulthood.  https://medlineplus.gov/genetics/condition/prickle1-related-progressive-myoclonus-epilepsy-with-ataxia

Clinical features

From HPO
Cerebellar ataxia
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Disease or Syndrome
Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).
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Mental or Behavioral Dysfunction
Dysarthric speech is a general description referring to a neurological speech disorder characterized by poor articulation. Depending on the involved neurological structures, dysarthria may be further classified as spastic, flaccid, ataxic, hyperkinetic and hypokinetic, or mixed.
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Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements.
Babinski sign
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Upturning of the big toe (and sometimes fanning of the other toes) in response to stimulation of the sole of the foot. If the Babinski sign is present it can indicate damage to the corticospinal tract.
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Sign or Symptom
An unintentional, oscillating to-and-fro muscle movement about a joint axis.
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A type of ataxia characterized by the inability to carry out movements with the correct range and motion across the plane of more than one joint related to incorrect estimation of the distances required for targeted movements.
Atonic seizure
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Disease or Syndrome
Atonic seizure is a type of motor seizure characterized by a sudden loss or diminution of muscle tone without apparent preceding myoclonic or tonic event lasting about 1 to 2 seconds, involving head, trunk, jaw, or limb musculature.
Sensory axonal neuropathy
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An axonal neuropathy of peripheral sensory nerves.
Generalized myoclonic seizure
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Disease or Syndrome
A generalized myoclonic seizure is a type of generalized motor seizure characterized by bilateral, sudden, brief (<100 ms) involuntary single or multiple contraction of muscles or muscle groups of variable topography (axial, proximal limb, distal). Myoclonus is less regularly repetitive and less sustained than is clonus.

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