My little brother, 18, has been living with Holoprosencephaly since he was a newborn. When he was born, he had a cleft lip and a hole in is palate. Though, it was easy fixed with surgery. When eating, his formula had to be mixed with minimal baby food, so it wouldn't pass right through him. Even then, he has grown healthy. He cannot do things on his own. An aide has to attend school with him. He takes life classes. My little brother tries to be independent, but it doesn't always work that way. His story isn't as severe as others that have Holoprosencephaly; however, it is a rare genetic disorder.
General Information
Holoprosencephaly is a structural anomaly of the brain. During development in the womb, the brain will fail to (or incompletely) separate into two separate hemispheres. The failing to separate normally occurs at the forebrain of the child. As it is a rare disorder, the numbers for a child born with HPE is very low. 5,000 - 10,000 live births occur with the child born with Holoprosencephaly. 1 in 250 pregnancies occur with the child forming HPE. Though, 3% of all fetuses survive to delivery. Most children do not live past 6 months of age depending on the severity of the HPE.
4 Types of HPE
- Alobar (severe)
- Semi-lobar (moderate)
- Lobar (mild) [Younger brother has this type]
- Middle Interhemispheric Variant (MIHV)
Causes of HPE
Cause of holoprosencephaly is not fully understood. 25-50% of all cases are associated with genetic abnormalities. Certain medications during pregnancy. Diabetes during pregnancy. History of miscarriage. Certain infections during pregnancy.
Genetics of HPE
25-50% of HPE cases are associated with structural or numerical chromosomal abnormalities. Abnormal numbers of chromosomes. Extra copy of chromosome 13 (called trisomy 13), an extra copy of chromosome 18 (called trisomy 18), and an extra copy of chromosome 15 (called trisomy 15). Genetic abnormalities associated with HPE may occur randomly or they may be passed down among families. Mutations in 11 genes. „Provide instruction for making proteins for normal fetal development. Common mutation in one of these four genes: SHH, ZIC2, SIX3, or TGIF1. SHH causes the eye field to separate into two distinct eyes. Mutation can cause a Cyclops like effect (forming one eye). SIX3 causes the formation of the lens of the eye.
Inheritance of HPE
Autosomal dominant pattern. Mutation from one parent who may or may not have mild features of the condition. „Result from a new gene mutation and occur in people with no history of the disorder in their family.
Symptoms of HPE
One central eye (cyclopia)
Small head
Cleft palate
Cleft lip
One front tooth
Flat nasal bridge
Large ears
Developmental Delay and intellectual disability
Malfunctioning pituitary gland
Diabetes Insipidus
Seizures
