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Microcephaly (from Neo-Latin microcephalia, from Ancient Greek μικρός mikrós "small" and κεφαλή kephalé "head" [2]) is a medical condition involving a smaller-than-normal head. [3] Microcephaly may be present at birth or it may develop in the first few years of life. [ 3 ]
The main signs of achalasia microcephaly syndrome involve the manifestation of each individual disease associated with the condition. Microcephaly can be primary, where the brain fails to develop properly during pregnancy, or secondary, where the brain is normal sized at birth but fails to grow as the child ages. [2]
[10] [11] However, an association has been established between normal variation in brain structure, as measured with MRI (i.e., primarily cortical surface area and total brain volume) but only in females, and common genetic variants within both the MCPH1 gene and another similarly studied microcephaly gene, CDK5RAP2.
A 20% increase in microcephaly frequency was seen in children with in-utero radiation exposure during the first trimester of the pregnancy (Miller 1956, 1968). Sensitivity to these radiations was seen to be predominantly high during the 7–15th week of gestation. [citation needed] Two pertinent points were observed during this study: [citation ...
Abnormal spindle-like microcephaly-associated protein, also known as abnormal spindle protein homolog or Asp homolog, is a protein that in humans is encoded by the ASPM gene. [5] ASPM is located on chromosome 1, band q31 (1q31). [6] The ASPM gene contains 28 exons and codes for a 3477 amino-acid-long protein. [6]
If ATR-X is suspected based on symptoms, diagnosis can be done via Genome testing. If the results are conclusive with ATR-X syndrome, female members of the same family will often be asked to partake in genome testing to see if anyone else in the family may possess this gene.
The combination of lissencephaly with severe congenital microcephaly is designated as microlissencephaly only when the cortex is abnormally thick. If such combination exists with a normal cortical thickness (2.5 to 3 mm [4]), it is known as "microcephaly with simplified gyral pattern" (MSGP). [5]
This results in an extra chromosome, making the haploid number 24 rather than 23. Fertilization of eggs or insemination by sperm that contain an extra chromosome results in trisomy, or three copies of a chromosome rather than two. [14] Trisomy 18 (47,XX,+18) is caused by a meiotic nondisjunction event.