Microdeletion syndrome

A genetic disorder caused by the deletion of a small chromosomal segment

Microdeletion syndrome is a genetic disorder characterized by the deletion of a small segment of a chromosome. These deletions can lead to a variety of developmental and physical abnormalities, depending on the specific genes that are lost. Microdeletion syndromes are often identified through genetic testing, such as fluorescence in situ hybridization (FISH) or comparative genomic hybridization (CGH).

Overview

Microdeletion syndromes are a subset of chromosomal deletion syndromes, where a small part of a chromosome is missing. These deletions can occur on any chromosome and can vary in size. The loss of genetic material can disrupt the function of multiple genes, leading to a range of clinical features.

Common Microdeletion Syndromes

Several well-known microdeletion syndromes have been identified, each associated with specific clinical features:

22q11.2 Deletion Syndrome

22q11.2 deletion syndrome, also known as DiGeorge syndrome or velocardiofacial syndrome, is one of the most common microdeletion syndromes. It is caused by the deletion of a small segment on chromosome 22. Clinical features can include congenital heart defects, cleft palate, immune deficiencies, and developmental delays.

Williams Syndrome

Williams syndrome is caused by a deletion on chromosome 7. It is characterized by distinctive facial features, cardiovascular problems, and developmental delays. Individuals with Williams syndrome often have a unique cognitive profile, with strengths in verbal abilities and weaknesses in visuospatial tasks.

Prader-Willi Syndrome

Prader-Willi syndrome results from a deletion on chromosome 15. It is associated with hypotonia, obesity, intellectual disability, and endocrine abnormalities. The syndrome is caused by the loss of paternal genes in the 15q11-q13 region.

Angelman Syndrome

Angelman syndrome is caused by a deletion on the maternal chromosome 15, in the same region as Prader-Willi syndrome. It is characterized by severe intellectual disability, lack of speech, seizures, and a happy demeanor.

Diagnosis

Microdeletion syndromes are typically diagnosed using genetic testing techniques. Fluorescence in situ hybridization (FISH) can be used to detect specific deletions, while comparative genomic hybridization (CGH) allows for the detection of larger deletions across the genome. Next-generation sequencing (NGS) is also increasingly used to identify microdeletions.

Management

Management of microdeletion syndromes is often multidisciplinary, involving specialists in genetics, cardiology, neurology, and developmental pediatrics. Treatment is symptomatic and supportive, focusing on addressing the specific medical and developmental needs of the individual.

Images

File:Chromosome deletion.png

Diagram of a chromosomal deletion.

Related pages

• Chromosomal deletion
• Genetic disorder
• Fluorescence in situ hybridization
• Comparative genomic hybridization