Snijders Blok-Campeau syndrome is a

genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...

caused by mutations in the CHD3 gene. It is characterized by impaired intellectual development,

macrocephaly Macrocephaly is a condition in which circumference of the human head is abnormally large. It may be pathological or harmless, and can be a familial genetic characteristic. People diagnosed with macrocephaly will receive further medical tests to ...

dysarthria Dysarthria is a speech sound disorder resulting from neurological injury of the motor component of the motor–speech system and is characterized by poor articulation of phonemes. In other words, it is a condition in which problems effectively ...

and

apraxia of speech Apraxia of speech (AOS), also called verbal apraxia, is a speech sound disorder affecting an individual's ability to translate conscious speech plans into motor plans, which results in limited and difficult speech ability. By the definition of ap ...

, and certain distinctive facial features. Snijders Blok-Campeau syndrome is typically a

de novo mutation A de novo mutation is any mutation/alteration in the genome of any organism (humans, animals, plant, microbes, etc.) that wasn't present or transmitted by their parents. This type of mutation (like any other) occurs spontaneously during the process ...

which generally occurs during the early embryonic stages of development or during the formation of the parent's

reproductive cells A gamete (; , ultimately ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also r ...

. This allows for

prenatal diagnosis Prenatal testing consists of prenatal screening and prenatal diagnosis, which are aspects of prenatal care that focus on detecting problems with the pregnancy as early as possible. These may be anatomic and physiologic problems with the health of ...

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 The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...

or similar conditions.

Cause

The CHD3 gene is required for

chromatin remodeling Chromatin remodeling is the dynamic modification of chromatin architecture to allow access of condensed genomic DNA to the regulatory transcription machinery proteins, and thereby control gene expression. Such remodeling is principally carried out ...

, a process that regulates gene expression. By allowing for the creation of

chromatin Chromatin is a complex of DNA and protein found in eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important roles in r ...

, the CHD3 gene affects how tightly DNA is packed into

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

s. 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 Medical genetics is the branch tics in that human genetics is a field of scientific research that may or may not apply to medicine, while medical genetics refers to the application of genetics to medical care. For example, research on the caus ...

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''".

References

Genetic diseases and disorders Genetics Intellectual disability Developmental disabilities Diseases and disorders Syndromes Syndromes affecting head size Speech disorders Disorders causing seizures Disorders of fascia Disorders of synthesis of DNA, RNA, and proteins Rare diseases Rare syndromes {{Genetic-disorder-stub