A case of suspected teratogenic holoprosencephaly

Clinical and Demographic Evaluation of a Holoprosencephaly Cohort From the Kyoto Collection of Human Embryos

Holoprosencephaly (HPE) is a genetically and phenotypically heterogeneous disorder involving developmental defects. HPE is a rare condition (1/10,000-20,000 newborns) but can be found as frequently as 1/250 among conceptions, suggesting that most HPE embryos are incompatible with postnatal life and result in spontaneous abortions during the first trimester of gestation. Beginning in 1961, the Kyoto University in Japan collected over 44,000 human conceptuses in collaboration with several hundred domestic obstetricians. Over 200 cases of HPE have been identified in the Kyoto collection, which represents the largest single cohort of HPE early stage embryo specimens. In this study, we present a comprehensive clinical and demographic evaluation of this HPE cohort prior to genomic analysis. The total percentage of the threatened abortion among HPE embryos in the Kyoto collection was 67%. Almost 20% of the women with embryos affected by HPE had experienced spontaneous miscarriage. In addition, there was a significant tendency that the mothers with HPE cases had fewer live births than the control. Moreover, in 70% of cases, the mother reported bleeding during pregnancy, a higher percentage than expected, indicating that most of the conceptions with HPE embryos tend to be terminated spontaneously. There were no differences in smoking between mothers with HPE affected and unaffected pregnancies; however, alcohol use was higher in women with pregnancies affected by HPE. In this study, we precisely characterize the phenotype and environmental influences of embryos affected by HPE allowing the future leveraging of genomic technologies to further understand the genetics of forebrain development. Anat Rec, 301:973-986, 2018. © 2018 Wiley Periodicals, Inc.

Risk factors for nonsyndromic holoprosencephaly: a Manitoba case-control study

Holoprosencephaly (HPE) is one of the most common developmental field defects, occurring in 1 in 250 conceptuses and in 1 in 10,000-20,000 live births. Nearly half of patients with HPE have a recognized syndrome or a single gene defect. However, little is known about the risk factors for the remainder with "nonsyndromic" HPE. In our case-control study, we examine factors associated with nonsyndromic HPE. We identified 47 patients with HPE from the genetics clinic database with an equal number of controls matched for gender and birthdate. Of the 47 patients, 23 were identified as nonsyndromic. No statistically significant differences were noted between the mean maternal and paternal ages of patients and controls. Factors associated with nonsyndromic HPE were: having an Aboriginal mother (unadjusted odds ratio [OR] 3.5, 95% confidence interval [CI] 1.1-11.1), an Aboriginal father (OR 12.8, 95% CI 3.0-55.1), at least one Aboriginal parent (OR 5.0, 95% CI 1.6-16.0), or two Aboriginal parents (OR 8.8, 95% CI 2.0-37.8), the presence of a family history of a midline facial defect (OR 8.2, 95% CI 1.5-45.2), and being of low socioeconomic status (OR 3.0, 95% CI 1.0-9.1). Having an Aboriginal background remained statistically significant after adjusting for low socioeconomic status. Other associations evaluated--history of prior spontaneous abortion, stillbirth, neonatal death, prepregnancy diabetes, infections during pregnancy, alcohol exposure, smoking, and substance abuse--were not significantly associated with nonsyndromic HPE. The use of periconceptional folic acid or vitamins was not associated with a lower risk of nonsyndromic HPE.

Non-genetic risk factors for holoprosencephaly

Holoprosencephaly (HPE) is a congenital defect of the brain characterized by incomplete cleavage of the embryonic forebrain into left and right hemispheres. Although a substantial proportion of cases of HPE can be attributed to genetic abnormalities, the etiology in many cases remains unknown, with non-genetic risk factors believed to be important contributors. Due to the low birth prevalence of this defect, it has proven difficult to conduct studies of sufficient size to identify risk factors with certainty. This article provides a summary of non-genetic risk factors for HPE that have been investigated in case reports and case series, animal studies, and epidemiologic studies, including maternal illnesses, therapeutic and non-therapeutic exposures, nutritional factors, and sociodemographic factors. The article also highlights challenges in study design and further areas for research to better understand the etiology of HPE.

Dydrogesterone use during pregnancy: overview of birth defects reported since 1977

Between 1977 and 2005, 28 cases of potential links between maternal dydrogesterone use during pregnancy and congenital birth defects were reported. The types of defects were very diverse, with no evidence of a pattern of abnormalities. The data do not provide evidence for congenital malformations associated with dydrogesterone use.

Cholesterol biosynthesis inhibited by BM15.766 induces holoprosencephaly in the rat

To confirm that blocking 7-dehydrocholesterol delta 7 reductase (7DHC reductase), as observed in Smith-Lemli-Opitz syndrome (SLOS), induces craniofacial defects, we tested BM15.766, which blocks 7DHC reductase but is chemically unrelated to the holoprosencephaly-inducing teratogen AY9944. Rats were given BM15.766 either in methylcellulose from days (D) 1 through D11 (3 treated groups: protocol A) or in olive oil from D4 through D7 (300 mg/kg/d: protocol B). The sera were sampled on D0, D3, and D5 or D6, D10, D14, and D21 to measure cholesterol and dehydrocholesterols in all groups and steroid hormones in protocol B. D21 fetuses showed the holoprosencephaly spectrum of malformations and the treated dams low cholesterol and accumulation of 7DHC, 8DHC, and trienols, as in SLOS-affected children. In the 3 dosage groups the malformations were dose-related and enzymatic cholesterol decreased to a plateau. The DHC reached 25-44% of the total sterols in the dams. In protocol B, one-third of the BM15.766-treated fetuses presented facial malformations and almost two-thirds pituitary agenesis. On D10, cholesterol reached a minimum and the DHC a maximum while estradiol 17 beta and progesterone were lowered, the latter decreasing in correlation with cholesterolemia. A sterol profile similar to that previously observed after AY9944 associated with a similarly high incidence of pituitary agenesis confirmed that time-limited inhibition of 7DHC reductase induces holoprosencephaly and that pituitary agenesis is the minor form of holoprosencephaly.

Holoprosencephaly: epidemiologic and clinical characteristics of a California population

Holoprosencephaly is a brain defect resulting from incomplete cleavage of the embryonic forebrain. It involves forebrain and facial malformations that can range from mild to severe. The epidemiology of holoprosencephaly is largely unknown. Published prevalence estimates have been derived from clinic-based case series, and suggested risk factors for holoprosencephaly have been identified in case reports, without confirmation from systematically conducted population-based studies. Using data from a population-based birth defects registry in California, we describe the epidemiologic and clinical characteristics of cytogenetically and phenotypically distinct types of holoprosencephaly. A total of 121 cases was identified among a cohort of 1,035,386 live births and fetal deaths. The prevalence of holoprosencephaly was 1.2 per 10,000 births (95% confidence interval 1.0-1.4 per 10,000). Of all cases, 41% (50/121) had a chromosomal abnormality, most commonly Trisomy 13. Among the 71 cytogenetically apparently normal cases, 18 had recognizable syndromes and the remaining 53 were of unknown cause. Among the cytogenetically abnormal cases, females had a greater risk than males (odds ratio = 2.3,95% confidence interval [1.2, 4.4]). Among the cytogenetically normal cases, increased risks were observed among Hispanic whites (OR = 1.8 [0.9, 3.6]) and cases whose mother was born in Mexico (OR = 2.2 [1.0, 4.5]). Approximately 46% of all cases had alobar holoprosencephaly, the most severe form of the forebrain malformation. The facial phenotype did not strongly predict the severity of the brain defect; however, severity was inversely correlated with length of survival. This study is the first to present findings based on such a large population-based series of infants/fetuses affected by holoprosencephaly, and demonstrates the importance of investigating the component subgroups of this rare phenotype.

Holoprosencephaly: examples of clinical variability and etiologic heterogeneity

Clinical variability and causal heterogeneity of holoprosencephaly is discussed in relation to several newborn infants with cyclopia (cases 4,5,6), cebocephaly (cases 2,3), and premaxillary agenesis (case 1). In subjects with holoprosencephaly, the presence of multiple malformations is an indicator of concomitant chromosome aberrations, as in present case 1 (Down syndrome) and case 3 (trisomy 13). Cases 5 and 6 are two monozygotic twins with the same type of cyclopia and alobar holoprosencephaly recognized by prenatal ultrasonography. The diagnostic importance of ultrasonographic, cytogenetic, and pathological studies is pointed out in view of etiologic evaluation, genetic counseling, and prevention of holoprosencephaly.

Holoprosencephaly: a developmental field defect

Holoprosencephaly refers to a spectrum of craniofacial malformations including cyclopia, ethmocephaly, cebocephaly, and premaxillary agenesis. Etiologic heterogeneity is well documented. Chromosomal, genetic, and teratogenic factors have been implicated. Recognition of holoprosencephaly as a developmental field defect stresses the importance of close scrutiny of relatives for mild forms such as single median incisor, hypotelorism, bifid uvula, or pituitary deficiency.