• Wu Peng, Shuxia Shi, Liqi Yang, and Deyun Liu.
• Department of Pediatrics, The Second Affiliated Hospital of Anhui Medical University, Hefei, China.
• Medicine (Baltimore). 2024 Jul 19; 103 (29): e39047e39047.

RationaleAllan-Herndon-Dudley syndrome (AHDS) results from a pathogenic variant in the hemizygous subunit of the SLC16A2 gene, which encodes monocarboxylate transporter 8 and follows an X-linked recessive pattern. AHDS manifests as neuropsychomotor developmental delay, intellectual disability, movement disorders, and thyroid hormone abnormalities. It is frequently misdiagnosed as cerebral palsy or hypothyroidism.Patient ConcernsA 9-month-old male infant exhibited poor head control, hypodynamia, motor retardation, hypertonic limbs, and thyroid abnormalities. Despite levothyroxine supplementation and rehabilitation therapy, no improvements were observed. Whole-exome sequencing identified a novel nonsense mutation in SLC16A2 (c.124G > T, p.E42X), which unequivocally established the diagnosis.DiagnosesAHDS was confirmed.InterventionsLevothyroxine treatment commenced early in infancy, followed by 3 months of rehabilitation therapy, starting at 5 months of age. The combined administration of levothyroxine and methimazole was initiated at 1 year and 10 months of age, respectively.OutcomesWhile improvements were noted in thyroid hormone levels, neurological developmental delays persisted.LessonsAHDS should be considered in patients presenting with atypical neurological features and thyroid hormone abnormalities such as elevated triiodothyronine and decreased thyroxine levels. The early utilization of exome sequencing aids in prompt diagnosis. The identified SLC16A2 nonsense mutation correlates with severe neurological phenotypes and adds to the spectrum of genetic variations associated with AHDS.Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.

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