{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,25]],"date-time":"2026-03-25T13:28:32Z","timestamp":1774445312131,"version":"3.50.1"},"reference-count":85,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,3,24]],"date-time":"2026-03-24T00:00:00Z","timestamp":1774310400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biomolecules"],"abstract":"<jats:p>Pyridoxine-dependent epilepsy due to ALDH7A1 deficiency (PDE-ALDH7A1) is a rare but treatable epileptic encephalopathy caused by disruption of lysine catabolism and secondary depletion of pyridoxal-5\u2032-phosphate (PLP). Although seizures are often controlled with pyridoxine supplementation, many patients continue to experience neurodevelopmental impairment, underscoring the importance of early diagnosis and improved therapeutic strategies. Central to both diagnosis and pathophysiology is the accumulation of lysine-derived metabolites, most notably \u03b1-aminoadipate semialdehyde (\u03b1-AASA), its cyclic Schiff base \u03941-piperideine-6-carboxylate (P6C), and pipecolic acid. These metabolites have become the biochemical hallmarks of PDE-ALDH7A1, linking ALDH7A1 pathogenic variants to PLP inactivation and neuronal dysfunction. However, their chemical instability and analytical requirements pose challenges for universal diagnostics and newborn screening. This review summarizes current understanding of lysine catabolism in health and disease, critically evaluates the diagnostic utility and limitations of classical biomarkers, and discusses emerging insights into their pathophysiological roles. We further highlight recent discoveries of novel, chemically stable biomarkers, including 6-oxopiperidine-2-carboxylic acid (6-oxo-PIP), 2-oxopropylpiperidine-2-carboxylic acid (2-OPP), and 6-hydroxy-2-aminocaproic acid (HACA), identified through advanced metabolomics approaches. These metabolites show promise for newborn screening and provide new mechanistic links between metabolic stress, seizure susceptibility, and ongoing neurological morbidity despite pyridoxine treatment. Collectively, advances in biomarker discovery are reshaping diagnostic strategies for PDE-ALDH7A1 and offering new perspectives on disease mechanisms, paving the way for earlier detection and the development of more effective, mechanism-based therapies.<\/jats:p>","DOI":"10.3390\/biom16040486","type":"journal-article","created":{"date-parts":[[2026,3,25]],"date-time":"2026-03-25T10:07:13Z","timestamp":1774433233000},"page":"486","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Classical and Emerging Biomarkers in Pyridoxine-Dependent Epilepsy (PDE-ALDH7A1): Implications for Early Diagnosis and Therapeutic Development"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0009-0008-9336-8862","authenticated-orcid":false,"given":"Muna","family":"Abedrabbo","sequence":"first","affiliation":[{"name":"Centre for Molecular Medicine and Therapeutics, BC Children\u2019s Hospital and the Department of Medical Genetics, University of British Columbia, 950 West 28th Avenue, Vancouver, BC V5Z 4H4, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Safiya","family":"Al Yazeedi","sequence":"additional","affiliation":[{"name":"College of Medicine and Health Sciences, Sultan Qaboos University, P.O. Box 36, Muscat 123, Oman"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Blair R.","family":"Leavitt","sequence":"additional","affiliation":[{"name":"Centre for Molecular Medicine and Therapeutics, BC Children\u2019s Hospital and the Department of Medical Genetics, University of British Columbia, 950 West 28th Avenue, Vancouver, BC V5Z 4H4, Canada"},{"name":"Incisive Genetics, 200\u2013980 George Street, Vancouver, BC V6A 0H9, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hilal","family":"Al-Shekaili","sequence":"additional","affiliation":[{"name":"Department of Biology, College of Science, Sultan Qaboos University, P.O. Box 36, Muscat 123, Oman"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"178","DOI":"10.1002\/jimd.12332","article-title":"Consensus guidelines for the diagnosis and management of pyridoxine-dependent epilepsy due to alpha-aminoadipic semialdehyde dehydrogenase deficiency","volume":"44","author":"Coughlin","year":"2021","journal-title":"J. Inherit. Metab. 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