Hypoplasia Là Gì

Pontocerebellar hypoplasia is a group of related conditions that affect the development of the brain. The term "pontocerebellar" refers to the pons and the cerebellum, which are the brain structures that are most severely affected in many forms of this disorder. The pons is located at the base of the brain in an area called the brainstem, where it transmits signals between the cerebellum and the rest of the brain. The cerebellum, which is located at the back of the brain, normally coordinates movement. The term "hypoplasia" refers to the underdevelopment of these brain regions.

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Pontocerebellar hypoplasia also causes impaired growth of other parts of the brain, leading khổng lồ an unusually small head kích thước (microcephaly). This microcephaly is usually not apparent at birth but becomes noticeable as brain growth continues khổng lồ be slow in infancy and early childhood.

Researchers have sầu described at least ten types of pontocerebellar hypoplasia. All forms of this condition are characterized by impaired brain development, delayed development overall, problems with movement, và intellectual disability. The brain abnormalities are usually present at birth, và in some cases they can be detected before birth. Many children with pontocerebellar hypoplasia live only into lớn infancy or childhood, although some affected individuals have sầu lived inlớn adulthood.

The two major forms of pontocerebellar hypoplasia are designated as type 1 (PCH1) & type 2 (PCH2). In addition lớn the brain abnormalities described above sầu, PCH1 causes problems with muscle movement resulting from a loss of specialized nerve cells called motor neurons in the spinal cord, similar to another genetic disorder known as spinal muscular atrophy. Individuals with PCH1 also have very weak muscle tone (hypotonia), joint deformities called contractures, vision impairment, & breathing & feeding problems that are evident from early infancy.

Comtháng features of PCH2 include a lack of voluntary motor skills (such as grasping objects, sitting, or walking), problems with swallowing (dysphagia), and an absence of communication, including speech. Affected children typically develop temporary jitteriness (generalized clonus) in early infancy, abnormal patterns of movement described as chorea or dystonia, và stiffness (spasticity). Many also have impaired vision and seizures.

The other forms of pontocerebellar hypoplasia, designated as type 3 (PCH3) through type 10 (PCH10), appear lớn be rare và have each been reported in only a small number of individuals. Because the different types have overlapping features, và some are caused by mutations in the same genes, researchers have proposed that the types be considered as a spectrum instead of distinct conditions.

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The prevalence of pontocerebellar hypoplasia is unknown, although most forms of the disorder appear khổng lồ be very rare.

Pontocerebellar hypoplasia can result from mutations in several genes. About half of all cases of PCH1 are caused by mutations in the EXOSC3 gene. PCH1 can also result from mutations in several other genes, including TSEN54, RARS2, and VRK1. PCH2 is caused by mutations in the TSEN54, TSEN2, TSEN34, or SEPSECS gen. In addition khổng lồ causing PCH1 and PCH2, mutations in the TSEN54 gen can cause PCH4 và PCH5. Mutations in the RARS2 ren, in addition khổng lồ causing PCH1, can result in PCH6. The remaining types of pontocerebellar hypoplasia are caused by mutations in other genes. In some cases, the genetic cause of pontocerebellar hypoplasia is unknown.

The genes associated with pontocerebellar hypoplasia appear khổng lồ play essential roles in the development and survival of nerve sầu cells (neurons). Many of these genes are known or suspected to be involved in processing RNA molecules, which are chemical cousins of DNA. Fully processed, mature RNA molecules are essential for the normal functioning of all cells, including neurons. Studies suggest that abnormal RNA processing likely underlies the abnormal brain development characteristic of pontocerebellar hypoplasia, although the exact mechanism is unknown. Researchers hypothekích thước that developing neurons in certain areas of the brain may be particularly sensitive sầu khổng lồ problems with RNA processing.

Some of the genes associated with pontocerebellar hypoplasia have sầu functions unrelated to RNA processing. In most cases, it is unclear how mutations in these genes impair brain development.

Learn more about the genes associated with Pontocerebellar hypoplasia

Additional Information from NCBI Gene:

This condition is inherited in an autosomal recessive sầu pattern, which means both copies of the gen in each cell have sầu mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated ren, but they typically vị not show signs & symptoms of the condition.