Question: How many people are affected by nonsyndromic holoprosencephaly ?
Answer: Nonsyndromic holoprosencephaly accounts for approximately 25 to 50 percent of all cases of holoprosencephaly, which affects an estimated 1 in 10,000 newborns.
Source: GHR

Question: What are the genetic changes related to nonsyndromic holoprosencephaly ?
Answer: Mutations in 11 genes have been found to cause nonsyndromic holoprosencephaly. These genes provide instructions for making proteins that are important for normal embryonic development, particularly for determining the shape of the brain and face. About 25 percent of people with nonsyndromic holoprosencephaly have a mutation in one of these four genes: SHH, ZIC2, SIX3, or TGIF1. Mutations in the other genes related to nonsyndromic holoprosencephaly are found in only a small percentage of cases. Many individuals with this condition do not have an identified gene mutation. The cause of the disorder is unknown in these individuals. The brain normally divides into right and left hemispheres during the third to fourth week of pregnancy. To establish the line that separates the two hemispheres (the midline), the activity of many genes must be tightly regulated and coordinated. These genes provide instructions for making signaling proteins, which instruct the cells within the brain to form the right and left hemispheres. Signaling proteins are also important for the formation of the eyes. During early development, the cells that develop into the eyes form a single structure called the eye field. This structure is located in the center of the developing face. The signaling protein produced from the SHH gene causes the eye field to separate into two distinct eyes. The SIX3 gene is involved in the formation of the lens of the eye and the specialized tissue at the back of the eye that detects light and color (the retina). Mutations in the genes that cause nonsyndromic holoprosencephaly lead to the production of abnormal or nonfunctional signaling proteins. Without the correct signals, the eyes will not form normally and the brain does not separate into two hemispheres. The development of other parts of the face is affected if the eyes do not move to their proper position. The signs and symptoms of nonsyndromic holoprosencephaly are caused by abnormal development of the brain and face. Researchers believe that other genetic or environmental factors, many of which have not been identified, play a role in determining the severity of nonsyndromic holoprosencephaly.
Source: GHR

Question: Is nonsyndromic holoprosencephaly inherited ?
Answer: Nonsyndromic holoprosencephaly is inherited in an autosomal dominant pattern, which means an alteration in one copy of a gene in each cell is usually sufficient to cause the disorder. However, not all people with a gene mutation will develop signs and symptoms of the condition. In some cases, an affected person inherits the mutation from one parent who may or may not have mild features of the condition. Other cases result from a new gene mutation and occur in people with no history of the disorder in their family.
Source: GHR

Question: What are the treatments for nonsyndromic holoprosencephaly ?
Answer: These resources address the diagnosis or management of nonsyndromic holoprosencephaly: - Gene Review: Gene Review: Holoprosencephaly Overview - Genetic Testing Registry: Holoprosencephaly 1 - Genetic Testing Registry: Holoprosencephaly 10 - Genetic Testing Registry: Holoprosencephaly 2 - Genetic Testing Registry: Holoprosencephaly 3 - Genetic Testing Registry: Holoprosencephaly 4 - Genetic Testing Registry: Holoprosencephaly 5 - Genetic Testing Registry: Holoprosencephaly 6 - Genetic Testing Registry: Holoprosencephaly 7 - Genetic Testing Registry: Holoprosencephaly 8 - Genetic Testing Registry: Holoprosencephaly 9 - Genetic Testing Registry: Holoprosencephaly sequence - Genetic Testing Registry: NODAL-Related Holoprosencephaly These resources from MedlinePlus offer information about the diagnosis and management of various health conditions: - Diagnostic Tests - Drug Therapy - Surgery and Rehabilitation - Genetic Counseling - Palliative Care
Source: GHR