Objective: To present a case study of a 32-year-old woman with pathogenic variant in KCJN10 gene exhibiting ataxia and dystonic posturing with recurrent severe hypokalemia and hypomagnesemia compatible with EAST syndrome.

Background: EAST (Epilepsy, Ataxia, Sensorineural deafness and Tubulopathy) syndrome is a channelopathy is an autosomal recessive disorder associated with pathogenic variants in KCJN10 gene. Patients could present with complex movement disorders, pyramidal signs, sensorineural hearing loss, impaired communication and intellectual disability. Its renal phenotype is a tubulopathy. [1,2]

Method: Case report

Results: A 32-year-old woman with delayed development of motor and intellectual milestones and a history of infantile-onset recurrent tonic-clonic seizures associated with severe hypokalemia and hypomagnesemia – a Gitelman-like phenotype – during the episodes. She developed appendicular and axial ataxia at the age of 15, with pyramidal signs and dystonic posturing of limbs and face. There was no family history of neurological or nephrological disorders. Whole-Exome Sequencing revealed a pathogenic KCJN10 variant (c.193C>T) compatible with the diagnosis of EAST syndrome. Patient is seizure-free after introduction of antiseizure medications and oral electrolyte replacement.

Conclusion: Early-onset seizures with movement disorders warrant a thorough evaluation, including assessment of electrolyte serum levels. The presence of hypokalemia and hypomagnesemia with ataxia and seizures should raise suspicion of a KCJN10 variant diagnosis, necessitating interdisciplinary collaboration between neurology and nephrology for optimal management. This case emphasizes the importance of recognizing electrolyte abnormalities as clinical clues to a final diagnosis, particularly in the context of movement disorders.

References: [1] Abdelhadi O, Iancu D, Stanescu H, Kleta R, Bockenhauer D. EAST syndrome: Clinical, pathophysiological, and genetic aspects of mutations in KCNJ10. Rare Dis. 2016 Jun 1;4(1):e1195043.

[2] Bhowmick SS, Lang AE. Movement Disorders and Renal Diseases. Mov Disord Clin Pract. 2020 Aug 10;7(7):763-779. doi: 10.1002/mdc3.13005. PMID: 33043074; PMCID: PMC7534014.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/when-the-nephrologist-calls-ataxia-seizures-and-hypokalemia-east-syndrome-and-kcjn10-gene-mutation/