7p21.1 Microdeletion Encompassing the ACTB Gene in a Japanese Child: Longitudinal Clinical and Neuroimaging Findings.

We report a Japanese male with genetically confirmed 7p21.1 microdeletion encompassing ACTB, followed longitudinally from infancy to late childhood. The patient presented at 10 months of age with microcephaly, short stature, global developmental delay, bilateral esotropia, and atypical Y-shaped deep plantar creases. Early evaluations excluded congenital infections and chromosomal abnormalities. At age four years and eight months, a brain MRI revealed multiple cystic lesions in the deep white matter near the left lateral ventricular trigone and scattered punctate hyperintensities, which remained unchanged at age 11 years and 10 months. Developmental assessments demonstrated persistent cognitive impairment (developmental quotient (DQ): 73 at age two years; 65 at age seven years). He also had growth restriction (height -2.7 SD at final follow-up), without seizures or major systemic malformations. This case represents one of the few Japanese reports of 7p21.1 microdeletion encompassing ACTB with a detailed clinical course over more than a decade and highlights an uncommon neuroradiological finding, deep white matter cysts, which may broaden the recognized phenotype. Our findings underscore the diagnostic value of exome sequencing in children with syndromic developmental delay when conventional evaluations are inconclusive and the importance of careful physical examination in early infancy to detect subtle anomalies that may provide critical diagnostic clues.