Snijders Blok–Campeau syndrome is a rare autosomal 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 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. +CharacteristicsPercentageCharacteristicsPercentageDevelopmental disorder100% Flexible ligaments40%Speech delay or disorder100% Central nervous system abnormalities39% Intellectual disability 95% Male genital abnormalities35% Low muscle tone 92% Autism or autism-like features33% Large or prominent forehead 85%Neonatal feeding problems31%Widely spaced eyes77%Strabismus30% Visual abnormalities 75%Seizures21%Thin upper lip74%Congenital heart disease21%Broad nasal bridge71%Missing teeth16% Macrocephaly 58%Hearing loss13%Deep set eyes54%Microcephaly5%
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".
Treatment There is no available cure for the syndrome, and treatment is supportive.
In 2026, successful trials of gene therapy in mice and monkeys were reported by Zilong Qiu and his team at the Shanghai Jiao Tong University School of Medicine, in the journal Nature. It was subsequently discovered that a year before, Qiu had treated a six-year-old girl at Xinhua Hospital in Shanghai using engineered viruses to carry the corrected gene into the spinal fluid. The girl died of thrombotic microangiopathy several days later.
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