snijders blok–campeau syndrome snijders blok–campeau syndrome snijders blok–campeau syndrome is a genetic disorder caused by mutations in the chd3 gene. it is characterized by impaired intellectual development, macrocephaly, dysarthria and apraxia of speech, and certain distinctive facial features. snijders blok–campeau syndromeother namessnibcps, iddmsfan image displaying 18 individuals who have snijders blok-campeau syndromesymptomsintellectual disability, macrocephaly, distinctive facial featuresusual onsetbefore birthdurationlife longcausesmutations in the chd3 genefrequencyapproximately 60 cases described in scientific literature, with an estimated 150 diagnosed worldwide snijders blok–campeau syndrome is typically a de novo mutation which generally occurs during the early embryonic stages of development or during the formation of the parent's reproductive cells. this allows for prenatal diagnosis. signs and symptoms snijders blok–campeau syndrome almost always comes with both physical and intellectual disabilities. those with the condition will typically have trouble in the development of speech and language. around one half typically have some form of macrocephaly, while around one third show signs of autism or similar conditions. characteristics percentage characteristics percentage developmental disorder 100% flexible ligamets 40% speech delay or disorder 100% central nervous system abnormalities 39% intellectual disability 95% male genital abnormalities 35% low muscle tone 92% autism or autism-like features 33% large or prominent forehead 85% neonatal feeding problems 31% widely spaced eyes 77% strabism 30% visual abnormalities 75% seizures 21% thin upper lip 74% congenital heart disease 21% broad nasal bridge 71% missing teeth 16% macrocephaly 58% hearing loss 13% deep set eyes 54% microcephaly 5% cause the chd3 gene is required for chromatin remodeling, a process that regulates gene expression. by allowing for the creation of chromatin, the chd3 gene affects how tightly dna is packed into chromosomes. a mutation of the chd3 gene changes the amount of chromatin produced, causing over or underexpression of other genes. history due to the rarity of the condition, with only approximately 60 cases documented in scientific literature, snijders blok–campeau syndrome was only discovered in 2018 by clinical geneticist lot snijders blok and clinician-scientist philippe m campeau. the mutation was first documented in the paper "chd3 helicase domain mutations cause a neurodevelopmental syndrome with macrocephaly and impaired speech and language".