Mitochondrial Dysfunction in a Patient with 8q21.11 Deletion and Charcot-Marie-Tooth Disease Type 2K due to GDAP1 Haploinsufficiency.

Unbalanced chromosomal rearrangements typically cause multiple organ system involvement including neurodevelopmental deficits. It is atypical, however, to experience developmental and neurological regression. We describe a female with intellectual disability, failure to thrive, short stature, multiple congenital anomalies, and dysmorphic features and a previously diagnosed de novo 8q21.11 deletion at the age of 7. However, at the age of 11, she experienced neurological and developmental regression. The GDAP1 gene encoding ganglioside-induced differentiation-associated protein 1 was deleted in the patient as a part of the contiguous gene syndrome. We argue that haploinsufficiency of GDAP1 could have contributed to the proband's regression based on its involvement in mitochondrial function and a signal transduction pathway in neuronal development.