13q34 deletions – or deletions at the terminal segment of the long arm of chromosome 13 – are very rare. Therefore, symptoms of 13q34 deletions are not well described. This article reports two brothers with 13q34 deletions, whose symptoms include intellectual disability, epilepsy, and genitourinary tract defects. From these cases, the article hopes to reveal some common symptoms for these types of deletions, as well as the potential genes that may be causing these symptoms when lost.
According to the authors only six patients with 13q34 deletions have been reported so far. The two patients described in this article have smaller 13q34 deletions when compared to previously-studied patients. They share similar symptoms as other patients, including intellectual disability, growth delay, facial dysmorphism, and microcephaly (an abnormally small and underdeveloped head). However, they do not have the cardiac defects that the patients with larger deletions exhibited, suggesting that the genes affected by the larger deletions were unaffected in the patients in this current study.
There are 16 genes that are within the 13q34 deletion region of these two cases. Of particular interest are the genes SOX1 and ARHGEF7, which may be involved in the epilepsy symptoms when lost. It is known that both these genes interact with other genes that are involved in epilepsy symptoms (some of which include CTNNB1 and GRIN2D for SOX1 , and TSC1 and ITPA for ARHGEF7 ). ARHGEF7 also interacts with genes involved in proper brain development and function. Therefore, deletion of either one of these genes could be contributing to the epilepsy and intellectual disability symptoms, but more research needs to be conducted before conclusions can be drawn.
The two patients examined in this article give further evidence that the loss of genes SOX1 and ARHGEF7 is likely contributing to epilepsy and intellectual disability.
Orsini, et al. “Generalized epilepsy and mild intellectual disability associated with 13q34 deletion: A potential role for SOX1 and ARHGEF7 ”. Seizure 2018, v. 59, 38-40.
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