What causes semi lobar holoprosencephaly?
Holoprosencephaly can be caused by mutations in any of at least 14 different genes; chromosome abnormalities; or agents that can cause birth defects ( teratogens ). It may also be a feature of several unique genetic syndromes . In many cases, the exact cause is unknown.
What affects holoprosencephaly?
Nonsyndromic holoprosencephaly is an abnormality of brain development that also affects the head and face. Normally, the brain divides into two halves (hemispheres ) during early development. Holoprosencephaly occurs when the brain fails to divide properly into the right and left hemispheres.
What is the genetic cause of holoprosencephaly?
The most common chromosomal abnormality associated with HPE is when there are 3 copies of chromosome 13 (trisomy 13), although a number of other chromosomal changes can also cause holoprosencephaly. In other children, holoprosencephaly is due to a change in a specific gene.
What causes holoprosencephaly in pregnancy?
Sometimes HPE can be caused by environmental causes. The most common known cause of HPE in humans is maternal type 2 diabetes mellitus. In pregnancies of diabetic mothers, the chance for HPE to occur is about 1%. Approximately 25%-50% of individuals with HPE have a chromosome error as the underlying cause of their HPE.
How does holoprosencephaly cause a single lobed brain?
Holoprosencephaly is a disorder caused by the failure of the prosencephalon (the embryonic forebrain) to sufficiently divide into the double lobes of the cerebral hemispheres. The result is a single-lobed brain structure and severe skull and facial defects.
Is there a rare case of alobar holoprosencephaly?
We report a severe case of alobar holoprosencephaly diagnosed at 38 weeks, associated with cebocephaly, microcephaly, and craniosynostosis. The main knowledge added by this case is the late ultrasound diagnosis and chromosomal analysis that revealed a very rare abnormality (45X/46,XX/47,XX) with mosaicism at chromosome 18.
What are the symptoms of holoprosencephaly after birth?
After birth, the diagnosis of the fetus confirmed holoprosencephaly with facial anomalies and demonstrated repeated tonic-clonic seizure, severe respiratory failure, cyanosis, decreased muscle tone, palor, and apnea. Laboratory examination of the newborn revealed acidosis and a prolonged of prothrombin time.
Where does holoprosencephaly occur in the United States?
In the United States, seemingly higher prevalences have been reported in Hispanic, African-American, and Pakistani ethnicities, likely attributable to decreased prenatal diagnosis and termination rates in these groups 6).