11q- Deletion - An Overview

Introduction

11q deletion is a genetic disorder caused due to absent or missing genes from chromosome 11. Genetic errors were noted to cause this disorder. Amongst the various type of genetic errors, deletion is responsible for 11q deletion. The other name for 11q deletion is Jacobsen syndrome. In 1973, 11q deletion was first detected and named Jacobsen syndrome after the Danish researcher who identified it. Gene deletion in chromosomes is divided into ranges of errors, including small to large deletions. Therefore, the severity of any genetic disorder, including 11q deletion, depends on the range of the deletion, either small or large. Researchers have proved that large deletion portrays more severe symptoms in comparison to small deletion.

What Is Meant by Chromosomal Aberrations?

Chromosomal aberrations are errors in genetic expression, and it leads to structural and numerical abnormalities. The chromosomal aberration is also known as chromosomal mutation. Structural aberrations include structural abnormalities, and ploidy changes or numerical aberrations include numerical changes or abnormalities. Structural aberrations comprise the errors in which a chromosome or gene segment is extra, lost, or located in some other region (translocated). There are four types of chromosomal aberrations identified by genetic researchers, namely:

• Deficiency or deletion.

• Duplication.

• Inversion.

• Translocation.

What Is the Deletion Type of Chromosomal Aberration?

Chromosomal aberration is classified into four types, and deletion is one of them. In the deletion type of genetic mutation, a chromosome segment, including its genes, is missing. Genetic researchers have classified deletion type of chromosomal aberration into four types as follows:

• Terminal deletion.

• Intercalary deletion.

• Homozygous deletion.

• Heterozygous deletion.

In terminal deletion, the segment of chromosomes or genes is missing from the terminal part with a single break. Intercalary deletion describes the type of genetic error in which the segment of a chromosome or the genes are missing from the between. Two breaks in the segment mark the identification of the intercalary type of deletion. Homozygous deletion describes the loss of chromosome segments or genes from the homologous chromosome pair, and in the heterozygous type of deletion, chromosomal segments or genes are lost from any homologous chromosome pair.

Deletion is the type of genetic error that explains the loss of genetic material and genes and is associated with deleterious effects, including abnormal features in individuals suffering from this disorder. Every genetic disorder is defined by a specific set of signs and symptoms.

How Is 11q Deletion Caused?

11q deletion disorder is caused due to deletion of genetic material in chromosome 11. In most cases, the deletion of genetic material is noted in the tip of chromosome 11. Larger the deletion error, severe the signs and symptoms. Multiple genes, which include around 170 to 340 genes, are noted to be involved in genetic errors like deletion. At present, all genes are not extensively studied.

What Are the Clinical Features of Jacobsen Syndrome?

Wide variations in signs and symptoms are noted in Jacobsen syndrome. The following are the most commonly reported clinical features:

• Growth retardation.

• Delayed speaking abilities.

• Motor skills are poorly developed, and individuals face difficulty in sitting and standing, which causes difficulty in carrying out daily activities.

• Attention deficit hyperactivity disorder is a commonly noted feature in 11q deletion. It is a neurodevelopmental disorder that gets diagnosed at an early age. Children suffering from this disorder have difficulty concentrating, get easily distracted, and have delayed thinking abilities; children suffering from this disorder have difficulty learning the alphabet, spelling, and mathematical tables.

• Compulsive behavior such as shredding papers is common altered behavior in these children.

• Impaired socializing skills are also noted in these children, similar to autistic children.

• Heart and kidney disorders are also quite frequently diagnosed in these individuals.

Following are a few distinctive features that are noted in children suffering from Jacobsen syndrome (11q deletion disorder):

• Ears are small and low set.

• Eyes are wide apart from each other.

• Ptosis (drooping eyelids).

• Epicanthal folds are the type of eye feature that is prominently noted.

• Broad nasal bridge.

• The corners of the mouth are downturned, giving a crying appearance to the child.

• The upper lips of the child are thin, and broader lower lips are noted.

• Lower jaw bones in these children are small in size, and this is due to delayed growth.

• Macrocephaly is a large head size and is a common feature that can be noted in these individuals.

• The forehead in these individuals has a typical pointed appearance.

• These individuals also suffer from bleeding disorders. Paris-Trousseau syndrome is a platelet disorder that is present in these individuals. Hence, they risk easy bleeding and bruising their entire life.

• Due to delayed development, these individuals are short-statured.

• Ear and sinus infections are quite frequent in these individuals.

The life expectancy of these individuals is very average, but there are cases recorded in the medical literature that state the individual's survival up to adulthood.

Is 11q Deletion Disorder Inherited?

11q deletion disorder is not an inherited disorder, and it results from the genetic error that occurs during genetic expression. This occurs due to a random error during the reproductive cell's production of eggs and sperm or during early fetal development. Affected people have no history of a similar disorder in the past, but they may pass this chromosomal deletion to their children. Five to ten percent of individuals even inherit these chromosomal deletion errors from parents who are unaffected by 11q deletion disorder. These chromosomal abnormalities produce symptoms that are typical of this genetic error.

What Are the Management Protocols for 11q Deletion Disorder?

A definite treatment protocol is not yet discovered. Providing symptomatic relief that eases these individuals' daily activities is the primary focus for management during the initial phase. Psychiatrists aim to reduce the symptoms of behavioral disorders and improve these individuals' socializing skills. Physiotherapists seek to improve 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 so that the caries rate is reduced. Specialized doctors treat individuals with severe signs and symptoms, including heart and kidney disorders, with utmost care.

Conclusion

11q deletion disorder or Jacobsen disorder is a rare genetic disorder caused due to deletion of genetic material in chromosome 11. The signs and symptoms vary widely; thus, clinicians should thoroughly examine the patients. Solid treatment and protocol are not available, but various research is going on in medical genetics to treat this disorder. Genetic mapping and targeted gene therapy are being extensively studied for their application in diagnosing and treating rare genetic disorders like Jacobsen syndrome.