Trisomy of the short arm of chromosome 12 (trisomy 12p) is a rare chromosomal abnormality causing dysmorphic features, congenital anomalies, intellectual disabilities, developmental delays, and seizures. Detailed information regarding the types of seizures is scarce owing to the low incidence of seizures. In contrast, 18p deletions and seizures are rare. Previous reports on trisomy 12p or monosomy 18p are limited, and little is known about epilepsy in children with trisomy 12p or monosomy 18p. Here, we report a case of 46,XX,der(18)t(12;18)(p11.2;p11.2) with repeatedly disturbed consciousness accompanied by alternating hemiplegia, corresponding to the electroencephalogram findings. G-banding of the parents showed balanced translocation of the mother. The last hospitalization occurred when the patient was 12 years old and presented with disturbed consciousness and left-sided hemiplegia. Electroencephalogram showed continuous 1 to 2 Hz slow waves in the right hemisphere and a theta burst in the left hemisphere. Based on the genes on chromosomes 12 and 18, the symptoms seemed to be related to partial trisomy 12p. Our case suggests the possibility of a novel seizure phenotype associated with trisomy 12p.

A.K. and H.Y. designed and conceptualized the report and drafted the manuscript for intellectual content. H.H. analyzed and interpreted the genetic data and revised the manuscript for intellectual content. S.O. and S.T. analyzed and interpreted the data and revised the manuscript for intellectual content. K.N. and H.N. designed and conceptualized the study and revised the manuscript for intellectual content. All authors approved the final manuscript as submitted and agreed to be accountable for all aspects of this work.

Received: 04 January 2024

Accepted: 27 November 2024

Article published online:
27 December 2024

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