Beck–Fahrner syndrome
Ultra-rare genetic disorder from TET3 gene variants.
Beck–Fahrner syndrome (also called BEFAHRS or TET3 deficiency) is an extremely rare genetic condition resulting from harmful changes in the TET3 gene. The disorder arises when these genetic variants disrupt DNA demethylation during early embryonic development—a key epigenetic process that supports nervous system formation. It can appear spontaneously or be passed down in an autosomal dominant pattern. Diagnosis relies on molecular and genetic testing alongside typical symptoms. Care is supportive, focusing on quality of life through developmental and behavioral therapies, educational support, and monitoring by specialists such as geneticists, developmental pediatricians, neurologists, and various therapists. As of 2023, around 50 people worldwide have been diagnosed.
The condition’s features are often summarized by the mnemonic BEFAHRS: behavioral differences, epilepsy, facial features, autistic features, hypotonia, retardation of psychomotor development, and size differences. Most individuals experience global developmental delay, slow progress in mental and physical skills, delayed speech, and trouble with fine and gross motor tasks. Intellectual and learning disabilities are common, and over two-thirds of those affected have syndromic autism or social communication disorder. Other observed behavioral issues include ADHD, obsessive-compulsive tendencies, anxiety, depression, and psychosis. Low muscle tone is most noticeable in infancy, leading to feeding problems and constipation, and later hindering speech and motor development. Epilepsy or seizure disorders affect more than a third of individuals; some also have motor or movement disorders. Eye problems can cause vision, movement, or alignment issues, and hearing loss may occur. Brain imaging sometimes shows benign malformations. Facial features are often similar: a long face with a broad forehead, open-mouth appearance, protruding ears, arched eyebrows, and a high-arched palate. Musculoskeletal issues include kyphosis, scoliosis, hyperflexible joints, hip misalignment, and flat feet. Some individuals show overgrowth—larger head size and tall stature—occasionally linked to enlarged kidneys or heart; others show undergrowth with smaller head size and short stature. Less common findings include congenital heart defects, pyloric stenosis, inguinal hernia, hypospadias, and undescended testis.
The TET3 gene
- field
- Medical genetics
- known_for
- First human disorder of DNA demethylation
- prevalence
- Approximately 50 diagnosed individuals as of 2023
- inheritance
- Autosomal dominant; can occur spontaneously or be inherited
- gene
- TET3 (chromosome 2p13.1)
Quick Facts
- Specialty
- Medical genetics and genomics
Facts from the source article.
Lore & Background
Beck–Fahrner syndrome is characterized by a mnemonic encompassing its prominent features: behavioral differences, epilepsy, facial features, autistic features, hypotonia, retardation of psychomotor development, and size differences. The most common neurodevelopmental symptoms include global developmental delay, slow progress in mental and physical activities, delayed speech, and difficulties with fine and gross motor skills. Intellectual and learning disabilities are common, and more than two-thirds of affected individuals have syndromic autism or social communication disorder. Decreased muscle tone is most noticeable in early life, causing feeding difficulties and constipation in infants, and further impeding speech and motor skills in children. Epilepsy affects over one-third of individuals, and some encounter motor and movement disorders. Eye involvement can lead to vision, movement and alignment issues, and ear involvement may result in hearing loss. Most individuals exhibit similar facial features, including a long face with a broad forehead, an open mouth appearance, protruding ears, arched eyebrows and a high-arched palate. Musculoskeletal abnormalities encompass kyphosis, scoliosis, hyperflexible joints, hip misalignment and flat feet. Overgrowth may manifest with larger head size and tall stature; rarely this may be correlated with enlarged kidneys and heart. Conversely, undergrowth has also been reported, associated with smaller head size and short stature.
Reader's Guide
Beck–Fahrner syndrome is significant as the first delineated human disorder of DNA demethylation, highlighting the critical role of epigenetic regulation in neurodevelopment. The TET3 gene encodes an enzyme that converts 5-methylcytosine to 5-hydroxymethylcytosine, initiating active DNA demethylation during embryogenesis. Pathogenic variants disrupt this process, leading to DNA hypermethylation and impairing nervous system development. Diagnosis involves molecular and genetic testing, with exome sequencing recommended due to limited availability of TET3 gene analysis on multigene panels. A distinct DNA methylation pattern (episignature) unique to TET3 variants can be assessed through whole blood genome-wide DNA methylation analysis, serving as a tool to confirm pathogenicity of variants of uncertain significance. Management is supportive, coordinated by medical genetics and developmental pediatrics, involving a multidisciplinary team. Early interventions such as autism therapies, speech therapy, physical and occupational therapy, and assistive technology can help manage symptoms. Genetic counseling educates families about the condition, assesses risk, and offers guidance on family planning and prenatal testing. The condition shares clinical findings with several other genetic disorders, and there is no consensus on diagnostic criteria.
Did You Know?
- Beck–Fahrner syndrome was the first human disorder of DNA demethylation to be delineated.
- As of 2023, approximately 50 individuals have been diagnosed with Beck–Fahrner syndrome.
- The condition can occur spontaneously or be inherited in an autosomal dominant manner.
- A distinct DNA methylation pattern (episignature) unique to TET3 variants can be assessed through whole blood genome-wide DNA methylation analysis.
More in Diseases named after discoverers 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record