Bosch–Boonstra–Schaaf optic atrophy syndrome
Rare genetic syndrome with developmental delay and visual impairment.
Bosch–Boonstra–Schaaf optic atrophy syndrome (BBSOAS) is a rare disorder inherited in an autosomal dominant pattern. Its main features are developmental delay, intellectual disability, and reduced visual sharpness.
Everyone diagnosed so far has had developmental delay and intellectual disability, with IQ scores ranging from 48 to 74, along with decreased visual acuity. Eye problems can include small or pale optic discs, disc excavation, strabismus, and latent nystagmus. Other signs vary but may involve the face—such as protruding ears, helical anomalies, a small nasal ridge, high nasal bridge, upturned nose, epicanthal folds, or upslanting palpebral fissures—and the skeleton, including tapering fingers and hypotonia.
The condition stems from mutations in the NR2F1 gene (also called COUP-TF1), located on the long arm of chromosome 5 (5q15). This gene makes a protein that functions as a nuclear receptor and transcriptional regulator, acting as a homo- or heterodimer with two conserved domains: a DNA-binding domain and a ligand-binding domain. The mutation types are varied and include both missense variants and deletions.
There is a clear link between genotype and phenotype. Patients with loss-of-function variants, such as deletions, tend to have a milder form of the disorder, while those with missense variants in the DNA-binding domain typically show a more severe neurological presentation.
No cure exists, and treatment is supportive. BBSOAS is considered rare, with an estimated prevalence of 1 in 100,000 to 250,000 people worldwide, and more than 100 patients have been diagnosed. It was first described in 2014.
Quick Facts
- Causes
- mutations in the NR2F1 gene
Facts from the source article.
Lore & Background
All patients described with Bosch–Boonstra–Schaaf optic atrophy syndrome have suffered from developmental delay, intellectual disability (IQ range 48–74), and decreased visual acuity. Ocular abnormalities include small discs, pale discs, disc excavation, strabismus, and latent nystagmus. Other features are variable and include facial indicators such as protruding ears, helical anomalies, small nasal ridge, high nasal bridge, upturned nose, epicanthal folds, and upslanting palpebral fissures, as well as skeletal indicators like tapering fingers and hypotonia.
Reader's Guide
The condition is caused by mutations in the NR2F1 gene, which encodes a nuclear receptor and transcriptional regulator. It is inherited in an autosomal dominant manner, with a diverse variant spectrum including missense variants and deletions. A clear genotype-phenotype correlation exists: loss-of-function variants (e.g., deletions) produce a mild phenotype, while missense variants in the DNA binding domain result in a severe neurological phenotype. There is no curative treatment; management is supportive. The syndrome is rare, with an estimated prevalence between 1 in 100,000 and 250,000, and has been diagnosed in more than 100 patients worldwide. Its significance lies in illustrating how specific genetic changes in a transcriptional regulator can lead to a distinct neurodevelopmental and visual disorder, informing both diagnosis and genetic counseling.
Did You Know?
- The syndrome is caused by mutations in the NR2F1 gene, also known as COUP-TF1.
- Patients with loss-of-function variants show a mild phenotype, while those with missense variants in the DNA binding domain show a severe neurological phenotype.
- The condition was first described in 2014.
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