Beck–Fahrner syndrome

Beck–Fahrner syndrome, also known as BEFAHRS and TET3 deficiency, is an ultra-rare genetic disorder caused by pathogenic variants of the TET3 gene. The clinical presentation varies among individuals, but typically includes global developmental delay, slow progress in mental and physical activities, syndromic autism, decreased muscle tone, epilepsy and dysmorphic features. Pathogenic variants in the TET3 gene disrupt DNA demethylation during embryogenesis, an essential epigenetic process contributing to the early development of the nervous system. The condition can occur spontaneously or be inherited in an autosomal dominant manner.

Diagnosis involves molecular and genetic testing in the context of typical symptoms. Management is supportive, aimed at improving quality of life—typically involving developmental and behavioral therapies, educational support, and monitoring by specialists such as physician geneticists, developmental pediatricians, neurologists and different therapists. As of 2023, approximately 50 individuals have been diagnosed with Beck–Fahrner syndrome.