Prenatal diagnosis of Alagille syndrome

Alagille syndrome mutation update: Comprehensive overview of JAG1 and NOTCH2 mutation frequencies and insight into missense variant classification

Alagille syndrome is an autosomal dominant disease with a known molecular etiology of dysfunctional Notch signaling caused primarily by pathogenic variants in JAGGED1 (JAG1), but also by variants in NOTCH2. The majority of JAG1 variants result in loss of function, however disease has also been attributed to lesser understood missense variants. Conversely, the majority of NOTCH2 variants are missense, though fewer of these variants have been described. In addition, there is a small group of patients with a clear clinical phenotype in the absence of a pathogenic variant. Here, we catalog our single-center study, which includes 401 probands and 111 affected family members amassed over a 27-year period, to provide updated mutation frequencies in JAG1 and NOTCH2 as well as functional validation of nine missense variants. Combining our cohort of 86 novel JAG1 and three novel NOTCH2 variants with previously published data (totaling 713 variants), we present the most comprehensive pathogenic variant overview for Alagille syndrome. Using this data set, we developed new guidance to help with the classification of JAG1 missense variants. Finally, we report clinically consistent cases for which a molecular etiology has not been identified and discuss the potential for next generation sequencing methodologies in novel variant discovery.

Alagille syndrome and pregnancy

Alagille syndrome is an autosomal dominant multisystem disorder with an estimated frequency of 1 in 30 000. Only a small number of pregnancy outcomes have been described in women with this condition. The report details the pregnancy outcomes of two women with Alagille syndrome. We also review the literature pertaining to this syndrome in pregnancy and demonstrate a significant risk of adverse pregnancy outcomes.

Alagille syndrome: clinical perspectives

Alagille syndrome is an autosomal dominant, complex multisystem disorder characterized by the presence of three out of five major clinical criteria: cholestasis with bile duct paucity on liver biopsy, congenital cardiac defects (with particular involvement of the pulmonary arteries), posterior embryotoxon in the eye, characteristic facial features, and butterfly vertebrae. Renal and vascular abnormalities can also occur. Inter- and intrafamilial variabilities in the clinical manifestations are common. We reviewed the clinical features and management as well as the molecular basis of Alagille syndrome.

Ultrasonography evaluation of infants with Alagille syndrome: In comparison with biliary atresia and neonatal hepatitis

OBJECTIVE

To evaluate the ultrasonography (US) features of Alagille syndrome (ALGS), as compared with biliary atresia (BA) or neonatal hepatitis (NH).

METHODS

Our study included 23 ALGS, 75 BA and 70 NH patients. The initial US images were retrospectively reviewed for gallbladder (GB) morphology with systemic classification, GB length and luminal area, presence of triangular-cord (TC) sign and hypertrophied hepatic-artery. The presence of anomalies associated with ALGS was evaluated. The diagnostic values of each finding and their combinations were evaluated.

RESULTS

Both ALGS (57%) and BA (79%) were more frequently associated with abnormal GB shapes than NH (19%, all P<0.001). The short and small GBs were more frequently observed in ALGS and BA than in NH (all P<0.001). None in the ALGS and NH showed TC sign, while 41% in the BA did (all P<0.001). Hypertrophied hepatic-artery was noted less frequently in both ALGS (13%) and NH (14%) than in BA (83%, all P<0.001). The combination of US criteria with associated anomalies increased the positive-predictive-value for ALGS.

CONCLUSION

Abnormal shaped GB with absence of the TC sign and hypertrophied hepatic-artery and presence of associated anomalies can be a differential point of ALGS.

Two- and three-dimensional prenatal sonographic diagnosis of Alagille syndrome

We describe a case of Alagille syndrome diagnosed by second-trimester ultrasound. Features included the characteristic prominent chin, single umbilical artery, and hemivertebrae. Three-dimensional imaging demonstrated classic butterfly vertebrae, which were not otherwise appreciable. Alagille syndrome may be detected by second-trimester ultrasound in the at-risk fetus.

Prenatal molecular diagnosis of inherited cholestatic diseases

OBJECTIVES

Progressive familial intrahepatic cholestasis (PFIC) and to a lesser extent, Alagille syndrome, often lead to end-stage liver disease during childhood. We report our experience of DNA-based prenatal diagnosis of PFIC1-3 and Alagille syndrome.

PATIENTS AND METHODS

Four molecular antenatal diagnoses were performed in 3 PFIC families and 17 in 11 Alagille syndrome families. DNA was isolated from chorionic villus or cultured amniocyte samples from women, without pregnancy complications.

RESULTS

All four foetuses with a family history of PFIC1, 2, or 3 were heterozygous for an ATP8B1, ABCB11, or ABCB4 mutation and pregnancies were continued. Three of the infants were healthy after birth, and 1 premature infant, who had an ABCB4 mutation, experienced transient neonatal cholestasis. Among the families with a history of de novo JAG1 mutation, none of the foetuses was mutated, versus 40% of those with a history of familial mutation. Of 4 pregnant women with a JAG1-mutated foetus, 3 cut short their pregnancy and 1 gave birth to a child with overt Alagille syndrome.

CONCLUSIONS

Molecular antenatal diagnosis of PFIC1-3 and Alagille syndrome is reliable because clinical outcome after birth corresponded to molecular foetal data.

Familial diseases revealed by a fetal anomaly

OBJECTIVES

The recognition of a fetal anomaly can lead to the same diagnosis being made in one of the asymptomatic parents unaware of the problem. We analyzed cases in which the discovery of a fetal anomaly led to the discovery of a genetic familial disorder.

METHODS

Families in which the recognition of a fetal anomaly led to the same diagnosis being made in one of the asymptomatic parents were included.

RESULTS

Twenty couples were included in the study. The fetal anomalies were cleft lip and palate (4), cardiac anomalies (2), cerebral anomalies (1), bilateral club feet with polyhydramnios, akinesia or camptodactily (5), nuchal anomalies (2), micromelia (3), polydactyly (2), and limited elbow extension (1). Genetic counselling helped establish nine maternal diseases as follows: Steinert disease (3), spinal muscular atrophy (1), antecubital pterygium (1), DiGeorge (1), Wardenburg type II (1), Charge (1) and Greig syndromes (1). Eleven paternal diseases were discovered, which were Noonan-like syndrome (1), paternal cervical anomalies (1), Goldenhar syndrome (1), dominant autosomal arthrogryposis (1), osteogenesis imperfecta (3), tuberous sclerosis (1), dominant transposition of great vessels (1), Weyers acrofacial dysostosis (1), and autosomal dominant holoprosencephaly (1). Twelve couples continued with pregnancy and eight opted for termination of pregnancy.

CONCLUSION

The fetus is central in giving the first insight into a familial disorder. It can reveal familial diseases undiscovered in the parent and help understand the mode of transmission of an anomaly, mainly the autosomal dominant diseases with variable expressions.