ADK deficiency without hypermethioninemia presenting as intractable epilepsy: a rare neurometabolic case and literature review.

ADK deficiency, an extremely rare inherited metabolic disorder affecting methylation, is likely underdiagnosed as a cause of epilepsy. The limited number of reported cases and variability in presentation, particularly the absence of hypermethioninemia, pose diagnostic challenges. We report an 11-year-9-month-old Indonesian boy with refractory seizures, developmental delay, dysmorphic features, hypotonia, and intellectual disability. Despite normal methionine levels, WES revealed a variant in the ADK gene, confirmed by Sanger sequencing; both parents were heterozygous carriers. Management with multiple antiseizure medications and a methionine-restricted diet reduced seizures, though development remained limited. This case report highlights the first genetically confirmed ADK deficiency case from Indonesia. A concise literature review of reported cases worldwide is also provided to contextualize this atypical phenotype and discuss current diagnostic and therapeutic considerations.

© 2026. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.