Clinical and Genetic Studies on Holoprosencephaly

Holoprosencephaly (HPE) is a defect of midline forebrain development that occurs soon after conception. It has a prevalence of 1 in 250 during early embryonic development, and 1 in 10,000 to 1 in 20,000 at term. In live born infants, the abnormalities associated with HPE are divided into three main categories: alobar, semilobar, and lobar HPE. A fourth variant, middle interhemispheric variant, has also been recognized. The purpose of this study is to increase our understanding of the genetic and clinical manifestations of HPE through detailed physical, psychological, developmental, neurologic, endocrinologic, and radiologic studies. We will examine the spectrum of clinical characteristics of HPE to facilitate early diagnosis and clinical management, including genetic counseling. Finally, we plan to assess the psychosocial impact of HPE on the family as a unit. Most patients and their families will be seen at the NIH Clinical Center. A subset may be examined outside the NIH, and a further subset, for the psychosocial studies, may be interviewed by phone.

• INCLUSION CRITERIA:

• Depending on their willingness to participate, subjects may enroll in DNA laboratory-only (98-HG-0249), psychosocial-only, or clinical-only. However, to conserve resources and meet study objectives, subjects with known mutations will be given priority in selection for extensive clinical studies. All races and genders are known to be at risk for HPE, anywhere in the world. Nationality or place of origin is not specific barrier to participation.
• Direct blood relatives (typically parents, and occasionally siblings of affected individuals) of patients with HPE are also eligible to participate.

Exclusion criteria

• Anyone unwilling to provide informed consent (for themselves as adults, or on behalf of their children as minors) or assent.
• Medical condition(s) or mental retardation are not in themselves reason for exclusion if in the judgment of the referring physician this would involve no more than minimal risk. We anticipate that children with mental handicaps would be included in the research population. We will make every effort to explain the study for the purpose of assent in a manner that the family feels is both age and developmentally appropriate for that child.
• We generally review a brief clinical description from the referring physician about a potential research subject to determine that the subject is appropriate to enter into the study. We reserve the right to exclude cases that are clearly not HPE or related to our direct research interests (e.g. HPE cases that are syndromic like Smith Lemli Opitz syndrome, Trisomy 13, Trisomy 18, drug-related, or teratogen-related). This almost never happens, and we would attempt to make referrals to a more appropriate investigator.

It is our intention to try to remove as many economic, cultural, geographic, racial, and gender barriers as we reasonably can to promote participation of HPE cases for research purposes.

Description and justification of clinical inclusion/exclusion criteria for environmental study arm control group (individuals with Williams syndrome) :

Participants must have a confirmed diagnosis of Williams syndrome caused by deletions in chromosome 7q11 involving the Williams-Beuren Syndrome Critical Region (WBSCR). Children should be less than 6 years of age to allow for improved maternal recall of prenatal

environmental exposures. The Williams syndrome cohort (PI: Dr. Beth Kozel; National Heart Lung Blood Institute) was chosen to allow for inherent biases in mothers who have children with multiple anomaly syndromes.