Introduction:
21q deletion is a genetic disorder caused due to absent or missing genes from chromosome 21. This disorder is caused due to an inborn error called deletion. The other names for 21q deletion are deletion 21q syndrome, monosomy 21q, 21q monosomy, and partial monosomy 21. Gene deletion in chromosome 21 ranges from small to large deletions. Therefore, the severity of symptoms of this disorder in large deletion is more in comparison to small deletion. Individuals suffering from this disorder have distinctive facial appearances, delayed growth, and intellectual abilities and are also retarded
What Is Meant by Chromosomal Aberrations?
Chromosomal aberrations explain structural and numerical abnormalities. The chromosomal mutation is the other name for chromosomal aberration. Structural changes or abnormalities are called structural aberrations, and numerical changes or abnormalities are called ploidy changes or numerical aberrations. Structural aberrations comprise the errors in which a chromosome or gene segment is extra, lost, or located in another region (translocated). Chromosomal aberrations have been classified into four types, namely:
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Deficiency or deletion.
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Duplication.
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Inversion.
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Translocation.
What Is the Deletion Type of Chromosomal Aberration?
Deletion can be defined as a chromosomal aberration type in which a chromosome segment and its genes are missing. Deletion is of the following four types namely:
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Terminal Deletion: In terminal deletion, there is one break with the segment of chromosomes or genes missing from the terminal part.
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Intercalary Deletion: In this deletion the type of genetic error which occurs is the segment of a chromosome or the genes missing in between. Two breaks in the segment can be seen in these sort of deletion error.
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Homozygous Deletion: It these deletion there will be loss of chromosome segments or genes seen in the homologous chromosome pair.
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Heterozygous Deletion: Heterozygous deletion speaks about the loss of chromosomal segments or genes seen in any homologous chromosome pair.
Deletion is a form of genetic error which causes loss of genetic material and genes associated with deleterious effects. This error can be displayed as signs and symptoms in every genetic disorder.
How Is 21q Deletion Caused?
21q deletion disorder is caused due to deletion of genetic material in chromosome 21 in the distal part of the long arm q. In most cases, the deletion of genetic material is noted in the terminal end of chromosome 21. More significant deletion shows more complex features than more minor deletion errors. Multiple genes are lost in this type of genetic error. At present, all genes are not studied. Researchers are working extensively on identifying the genes responsible for the disorder. Chromosomes are present in the nucleus of a cell present in the entire body of an individual. They are responsible for distinct characteristics in every individual. Each chromosome has two arms, one short and the other long. The short arm is denoted as p, and the long arm is denoted by q. Deleting the genetic material generally occurs due to a random error and is mostly not inherited.
Is 21q Deletion Disorder Inherited?
13q deletion disorder is not an inherited disorder, and it is caused due to genetic error. This occurs due to a random error during the reproductive cell's production of eggs and sperm or early fetal development. Affected people have no history of a similar disorder, but they may pass this chromosomal deletion to their children. Five to ten percent of individuals even inherit these chromosomal deletion errors from parents unaffected by 21q deletion disorder. Structural chromosomal aberrations are responsible for the development of these genetic disorders. These chromosomal abnormalities produce symptoms that are typical of this genetic error.
What Are the Clinical Features of the Genetic Disorder Due to Deletion Mutation?
The following are the most commonly reported general clinical features:
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Delayed growth.
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Altered development of speech.
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Motor skills such as sitting and standing are affected, which causes difficulty in carrying out daily activities.
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Attention deficit hyperactivity disorder is a commonly noted feature in 13q deletion. It is a neurodevelopmental disorder diagnosed in childhood and continues up to adulthood. Children suffering from this disorder have difficulty concentrating, get easily distracted, and have delayed thinking abilities. They have difficulty learning the alphabet, spelling, and mathematical tables.
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Compulsive behavior, such as shredding papers, is expected to alter behavior in these children.
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As seen in autism, impaired socializing skills are also noted in these children.
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Few individuals also suffer from heart and kidney disorders.
The following are a few distinctive features reported in individuals suffering from genetic disorders due to deletion:
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The back of the head appears to be flat.
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Hypertelorism (widely spaced eyes are commonly noted).
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The eyelid fold is slanted upward.
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Eyebrows have a high arch appearance.
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The midfacial region of the individual is generally flat in appearance.
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A short nose and flat nasal bridge are characteristic features in these individuals.
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Widened philtrum over the lips.
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Small lower jaw.
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Abnormally protruded lips.
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Ears are malformed.
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The palate has a high arch appearance.
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Presence of palatal clefts.
The genetic disorders caused due to deletion errors, namely, 6q deletion, 11q deletion, and 9p deletion, portray more or less similar characteristics, including delayed growth, retarded intellectual status, and distinctive facial appearance.
What Are the Management Protocols for 21q Deletion Disorder?
Researchers are working to search for a definite treatment protocol for this disorder. The doctors focus on providing symptomatic relief that eases these individuals' daily activities. Psychiatrists aim to reduce the symptoms of behavioral disorders and improve these individuals' socializing skills. Physiotherapists seek to enhance the motor skills of these individuals. So that they can sit, stand, and walk without any secondary support or minimum assistance. Dental practitioners aim to improve individuals' oral hygiene to reduce the caries rate. Specialized doctors treat individuals with severe signs and symptoms, including heart and kidney disorders, with utmost care.
Conclusion:
21q deletion disorder is a rare genetic disorder caused due to deletion of genetic material in chromosome 21’s long arm q. The signs and symptoms vary widely; thus, clinicians should thoroughly examine the patients. Solid treatment and protocol are unavailable, but various research is going on in medical genetics to treat this disorder. Genetic mapping and targeted gene therapy are extensively studied for their application in diagnosing and treating rare genetic disorders like 21q deletion.
