Deletion 15q13.3; 15q13.3 microdeletion syndrome ... (15q13.3 microdeletion syndrome) - Chromosome 15
The microdeletion 15q13.3 is a chromosomal abnormality where there is a small segment of the long arm, 15q13.3 position, one of the two chromosomes 15 in each possess cell in the body. The chromosomal abnormality can affect several genes found in this part of chromosome 15. However, some people with 15q13.3 microdeletion can no one have any representation. In general, individuals who lack this portion of chromosome 15 suffer from an impaired learning and / or physical development. According to the affected genes it increases the risk of mental retardation, seizures, behavioral problems and psychiatric disorders.
Clinical manifestations are variable but within a few concrete possibilities. Differences among individuals affected compared to others can be very marked, even when genetic involvement is the same. This fact has been observed even within the same family in which two members of this family genetic alteration. Therefore, each affected is unique and will have different clinical manifestations. The general characteristics and most common alterations are:
- Not usually obvious at birth defects observed.
- Intellectual disabilities. It is present in about half of those affected, characterized by mild or moderate difficulty learning, and only in some cases is intense. Children need help learning, requiring each separate aid.
- Delayed speech and language. Many of those affected may have delayed speech and in any case described has not come to speak. In other cases they understand but not expressed.
- Behavioral difficulties, with demonstrations within the autism spectrum or attention deficit hyperactivity disorder. Some children or adults, exhibit aggressive behavior, crisis schizophrenia, bipolar disorders with mood changes manic and depressive between.
- Delay learning to walk or sit.
- Some subtle differences in facial features.
- Increased risk of spontaneous seizures (seizures). When there are seizures, abnormalities are observed in the electroencephalogram.
- Brain or cardiac abnormalities.
- Many individuals with 15q13.3 microdeletion are completely healthy and compatible only detected when demonstrations are a son and genetic study is performed on the parents.
Most people with a microdeletion 15q13.3 have a deletion of a sequence of between 1.5 and 2 Mb in position q13.3 of chromosome 15. The exact size of the deleted region varies, and generally contains at least six genes. Signs and symptoms that may result from a microdeletion 15q13.3 are probably related to the loss of one or more genes in this region. However, it is unclear which genes absent contribute to the specific characteristics of the disease. Major genes that may be affected are: ARHGAP11B, MRMR15, MTMR10, TRPM1, KLF13, OTUD7A and CHRNA7. In some cases only missing the CHRNA7 gene, so it seems the gene involved in the demonstrations. TRPM1 seems most involved in visual impairment and KLF13 the most involved in cases of cardiac damages gene. Because some people with 15q13.3 microdeletion show no one signs or obvious symptoms, it is believed that other genetic or environmental factors may also be involved.
The microdeletion 15q13.3 is inherited as an autosomal dominant, which means that the absence of part of one of the two chromosomes 15, region 15q13.3 (microdeletion 15q13.3) is sufficient for the process is revealed. This defective chromosome 15 can be inherited from either parent, or parent. In approximately 75% of cases, individuals with inherited microdeletion 15q13.3 chromosome change of one of the two parents. In cases where one of the parents has 15q13.3 microdeletion in one of two chromosomes, the possibility of having a child with the microdeletion is theoretically 50% since the child inherits one of the two chromosomes 15 each parent has. As we discussed the presence of microdeletion is not always accompanied by demonstrations, so as a parent may have the microdeletion without presenting any manifestation, it can also happen that the son inherits and does not express any alteration. In the event that after having an affected child and one parent having the microdeletion 15q13.3, a second child might be affected, so it is recommended that a preinmplantacional diagnosis when in vitro fertilization is performed, or While prenatal diagnosis with chorionic villus sampling and testing to see if the microdeletion is present.
In other cases 15q13.3 microdeletion occurs without be present in either parent, appearing new (de novo) as a result of an error during the formation of sperm in males or ova of women, without any It has been induced by any environmental condition, food or lifestyle. This may occur during pairing chromosomes during formation of sperm and ova. In this phase the same chromosomes each possess two identical chromosomes that recognize sequences of the same chromosome, and there is exchange of genetic material (crossing over) after pairing. At this stage it may happen that upon separation, the resulting chromosomes are unequal to the cleavage of a part of chromosome microdeletion causing occur. In cases of this microdeletion occurred in this way (de novo), the probability that an affected have another sibling involvement is unpredictable and often it may occur is not known and it is considered that may have the same risk any other child in the general population.
Tests in IVAMI: IVAMI performed in the study of chromosome 15 by quantitative real - time PCR (qRT-PCR) to determine the existence of deletions in 15q13.3 position.
Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated card blood sample desiccated (IVAMI can mail the card to deposit the blood sample). In the case of prenatal diagnosis, chorionic villus sampling taken between 10 and 12 weeks gestation.