A Rare Case of Recurrent Disturbed Consciousness with Alternating Hemiplegia Associated with 46,XX,der(18)t(12;18)(p11.2;p11.2)

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 with alternating hemiplegia, corresponding to the electroencephalogram findings. G-banding of the parents showed balanced translocation of the mother. The last hospitalization occurred when our patient was 12 years old. She presented with disturbed consciousness and left-sided hemiplegia. Electroencephalography showed continuous 1–2 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.