Objective: To describe a case of a girl with progressive seizures, imbalance and regression due to a rare disorder and discuss the approach to the syndrome of progressive myoclonus ataxia.

Background: Neurological regression with involuntary movements in adolescence encompasses a broad diagnostic differential with variable prognoses.

Determining the specific aetiology is crucial yet challenging.

Method: A previously healthy 19-year-old female born of consanguineous parents presented with progressive symptoms for 4 years. At 15 years, she developed generalized tonic-clonic seizures. These were associated with occasional jerks in the morning on missing sleep. 1gm/day levetiracetam provided good control for one year. Then episodic jerking movements worsened and she developed a progressive gait imbalance associated with cognitive decline. Her neurological exam was notable for myoclonic jerks, truncal ataxia, and dysarthric speech. EEG showed irregular 2-2.5 Hz generalized spikes and slow background with occasional polyspike and wave discharges, concerning for an epileptic encephalopathy.

Results: Initial investigations including neuroimaging, ophthalmological exam, basic lab studies, and serum and CSF autoimmune panel were all normal. Her presentation raised suspicion for a range of progressive myoclonic epilepsy syndromes including Myoclonic epilepsy with ragged red fibres, Lafora disease, Neuronal Ceroid Lipofuscinosis, Unverricht-Lundborg disease, and Sialidosis. Genetic testing provided diagnostic clarity. Whole exome sequencing revealed a homozygous loss-of-function NHLRC1 mutation resulting in Lafora body disease, a form of progressive myoclonic epilepsy characterized by rapid neurological deterioration typically leading to death within 10 years of onset.

Conclusion: This case highlights the diagnostic challenge of involuntary movement disorders presenting in adolescence and demonstrates the utility of genetic testing in establishing prognosis and

recurrence risk to guide family planning. When jerks and stumbles become more than just clumsiness, an expanded differential and definitive diagnosis can help make sense of the senseless.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/when-jerks-and-stumbles-become-more-than-just-clumsiness/