What is 5p- syndrome?
5p- syndrome (also known as cri du chat syndrome) is a rare genetic disorder in which an individual’s genome is missing a portion of the short arm of a chromosome 5 normally present in humans.
The manner in which having 5p- syndrome impacts a given individual may vary, but the syndrome is commonly associated with low muscle tone, small head size, developmental delay, intellectual disability, and a variety of health ailments (including cardiac, respiratory, gastrointestinal, vision and auditory issues). A common symptom of 5p- syndrome at birth and in infancy is a cat-like cry, leading to the syndrome’s other name of cri du chat (French for “cry of the cat”) syndrome.
What are chromosomes and genes?
Chromosomes are thread-like structures made of protein and deoxyribonucleic acid (DNA) located inside the nucleus of animal and plant cells. Within humans, chromosomes exist in every cell and each chromosome has a short (p) arm and a long (q) arm, joined by a centromere. Human chromosomes are found in 23 pairs, with chromosome pairs 1 to 22 being autosomes (or looking the same within males and females) and chromosome pair 23 being XY for males and XX for females. Chromosomes are inherited from the parents of the individuals, with one chromosome in each pair contributed by the mother and one contributed by the father.
A given chromosome consists of a long strand of DNA containing many genes, which are distinct regions of DNA that encode function. These genes encode information that allow cells to produce proteins and other regulatory molecules necessary for the development and survival of the individual. There are an estimated 20,000 to 25,000 genes within the human genome, with genes spread across the 23 pairs of chromosomes. An individual has two copies of a given gene in the autosomal chromosome pairs 1 to 22.
What does the genome of a 5p- individual look like?
Just like everyone else, a 5p- individual inherits 23 chromosomes from their mother and 23 chromosomes from their father and these chromosomes are paired off accordingly. While a 5p- individual’s genome consists of the vast majority of a typical human genome, they are missing a portion of the short (p) arm of one of their fifth chromosomes (also referred to as a genetic deletion) in all or some of their cells. This results in the 5p- individual having only one copy of certain genes that reside on the fifth chromosome.
The amount and location of genetic material deleted from a 5p- individual’s fifth chromosome may vary greatly from person to person, with the deletion size measured in kb (thousands of base pairs) or mb (millions of base pairs). The entire length of the short (p) arm of the fifth chromosome is approximately 48 mb.
How common is 5p- syndrome?
5p- syndrome is a rare occurrence in live births, with only 1 in 35,000 to 50,000 babies being born with this syndrome. In the United States, only around 50 to 60 babies are born with 5p- syndrome in a given year.
What causes 5p- syndrome?
5p- syndrome is caused when an error occurs within the DNA replication process and genetic material is deleted from the fifth chromosome. The syndrome is generally not inherited (or passed down from generation to generation, although there are known cases of this occurring) and does not have any known contributing risk factors. Some studies suggest that the de novo deletions are generally paternal in origin.
How is 5p- syndrome treated?
Currently, there are no known cures for 5p- syndrome, but research to better understand the syndrome is ongoing. A variety of medical and therapeutic interventions can be used to help treat or mitigate the manifestations of the syndrome. For example, certain medical devices or surgeries may be recommended to mitigate impacts from certain physical ailments and Early Intervention therapies are recommended to give the 5p- babies and children a better starting point. 5p- individuals are encouraged to work with their medical professionals and therapists to establish a protocol of care that fits the needs of the 5p- individual and their caregivers.