Isochromosome Mosaic Turner Syndrome With Epilepsy and Developmental Abnormalities: A Case Report

Turner syndrome (TS) is a genetic disorder resulting from the partial or complete absence of one X chromosome in females. This condition gives rise to a spectrum of physical and developmental characteristics. Isochromosome mosaic Turner syndrome (IMTS) is a distinct form of this disorder, characterized by genetically different cell lineages, where one or more of the lineages contain an isochromosome X consisting of either p or q arms. While IMTS is relatively common, the relationship between IMTS and epilepsy along with developmental abnormalities remains an area of further investigation. An eight-year-old female presented with a seizure lasting more than 10 minutes, subsequent bilateral hand weakness, and an abnormal gait. Neurologic evaluation revealed a 24-hour amplitude-integrated electroencephalogram (EEG) demonstrating generalized sharp and slow waves increased with hyperventilation and left-sided delta activity. Both the brain magnetic resonance imaging (MRI) and repeated EEG, conducted while the patient was sedated, showed normal results. The patient was diagnosed with generalized epilepsy with underlying left hemispheric dysfunction. Early medical history revealed acid reflux, heightened sensitivity or aversion to certain textures, swallowing difficulties, attention-deficit/hyperactivity disorder, extremity clumsiness, and a focal seizure one year prior. In the following months, the patient continued having generalized tonic-clonic seizures and developed bilateral muscle weakness in her arms and legs. This prompted genetic testing, which revealed a karyotype of 45,X,t(17;20)(q23;p13)/46,X,I(X)(q10),t(17;20)(q23;p13) consistent with IMTS and an additional chromosomal translocation. This rare case highlights the potential association between IMTS and the development of epilepsy, emphasizing the importance of a multidisciplinary approach in evaluating TS patients. There is a need for further research that explores the genetic link between TS variants and epilepsy, as well as other intellectual disorders.