Table 3.

Hereditary Non-Progressive Myoclonic Disorders in the Differential Diagnosis of SCARB2-Related Action Myoclonus – Renal Failure Syndrome

GeneDisorderMOIClinical CharacteristicsComment
CACNB4
CILK1 (ICK)
CLCN2
EFHC1
GABRA1
GABRD 		Juvenile myoclonic epilepsy (JME) (OMIM PS254770)ADNormal neurologic exam; EEG background activity is undisturbed; myoclonus is not progressive. 1JME, which has a favorable outcome, should be considered at onset of myoclonus.
CNTN2
MARCHF6
RAPGEF2
SAMD12
STARD7
TNRC6A
YEATS2 		Cortical tremor syndrome 2 (OMIM PS601068)AD
AR		Adult-onset cortical myoclonus of extremities & seizures (mainly generalized tonic-clonic, less frequently myoclonic seizures or complex partial seizures) in 40% of affected personsCortical tremor syndrome, which usually has a favorable outcome, should be considered at onset of fine tremor.
SGCE SGCE myoclonus-dystonia (DYT11)AD 3Onset of myoclonus is usually in 1st or 2nd decade of life; myoclonus is subcortical in origin; ~50% of affected persons have segmental dystonia.The assoc of myoclonus & dystonia suggests DYT11. No other neurologic features (in particular ataxia & cognitive deficits) are assoc w/DYT11.

AD = autosomal dominant; AR = autosomal recessive; MOI = mode of inheritance

1.
2.

Also referred to as familial adult myoclonic epilepsy (FAME) & familial cortical myoclonic tremor associated with epilepsy (FCMTE)

3.

SGCE myoclonus-dystonia is inherited in an autosomal dominant manner with penetrance determined by the parental origin of the altered SGCE allele: an SGCE pathogenic variant on the paternally derived (expressed) SGCE allele generally results in disease; a pathogenic variant on the maternally derived (silenced) SGCE allele typically does not result in disease.

From: SCARB2-Related Action Myoclonus – Renal Failure Syndrome

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