Chromosome 15 disorders encompass a range of genetic conditions caused by alterations on chromosome 15. These alterations can include deletions, duplications, or imprinting errors affecting various genes located on this chromosome. The resulting conditions present with a wide spectrum of symptoms and severity.
Key Chromosome 15 Disorders:
Several well-known conditions are associated with chromosome 15 abnormalities:
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Prader-Willi Syndrome (PWS): This is one of the most common chromosome 15 disorders. It's typically caused by a deletion of genetic material from the paternal copy of chromosome 15 (paternal deletion). The condition is characterized by low muscle tone, intellectual disability, and an insatiable appetite leading to obesity. [Source: NHS, Mayo Clinic]
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Angelman Syndrome (AS): Another imprinting disorder, Angelman syndrome often results from a deletion of the maternal copy of chromosome 15, or from a faulty gene within this chromosome. Key features include developmental delays, intellectual disability, seizures, and a happy disposition with frequent laughter. [Source: Murdoch Children's Research Institute]
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15q Duplication Syndrome (dup15q): This disorder arises from a duplication of part of the long arm (q) of chromosome 15. It manifests with varying degrees of intellectual disability, hypotonia, and autism spectrum disorder. The severity depends on the size and location of the duplicated segment. [Source: GeneReviews]
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15q11-q13 Deletion Syndrome: This involves a deletion in a specific region of the long arm of chromosome 15. Symptoms can overlap with Prader-Willi syndrome and Angelman syndrome, depending on whether the paternal or maternal copy is affected. [Source: MedlinePlus Genetics]
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Chromosome 15 Ring: This rare condition is characterized by a circular structure of chromosome 15, resulting from a loss of genetic material at both ends. The symptoms are highly variable and often severe. [Source: NORD]
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Other less common disorders: Several other rarer conditions are associated with chromosome 15 abnormalities, including 15q13.3 microdeletion and 15q24 microdeletion. These disorders have unique clinical presentations and require specialized diagnosis. [Source: MedlinePlus Genetics]
Understanding the Genetics:
Many chromosome 15 disorders involve imprinting, a phenomenon where gene expression depends on the parent of origin. In Prader-Willi and Angelman syndromes, the deletion or mutation on one chromosome copy has significant effects depending on which parent contributed the affected copy. [Source: Frontiers in Pediatrics]
The specific genes impacted and the extent of the genetic change determine the severity and the specific symptoms of each condition.
