In-utero diagnosis of mucopolysaccharidosis type VII in a fetus with an enlarged nuchal translucency

Prenatal mucopolysaccharidosis VII: A novel pathogenic variant identified in GUSB gene

Clinical exome sequencing is a powerful approach to overcome the wide clinical and genetic heterogeneity of mucopolysaccharidosis. These data could be useful for prenatal diagnosis of MPS VII, genetic counseling, and preimplantation genetic testing.

A system-based approach to the genetic etiologies of non-immune hydrops fetalis

A wide spectrum of genetic causes may lead to nonimmune hydrops fetalis (NIHF), and a thorough phenotypic and genetic evaluation are essential to determine the underlying etiology, optimally manage these pregnancies, and inform discussions about anticipated prognosis. In this review, we outline the known genetic etiologies of NIHF by fetal organ system affected, and provide a systematic approach to the evaluation of NIHF. Some of the underlying genetic disorders are associated with characteristic phenotypic features that may be seen on prenatal ultrasound, such as hepatomegaly with lysosomal storage disorders, hyperechoic kidneys with congenital nephrosis, or pulmonary valve stenosis with RASopathies. However, this is not always the case, and the approach to evaluation must include prenatal ultrasound findings as well as genetic testing and many other factors. Genetic testing that has been utilized for NIHF ranges from standard chromosomal microarray or karyotype to gene panels and broad approaches such as whole exome sequencing. Family and obstetric history, as well as pathology examination, can yield additional clues that are helpful in establishing a diagnosis. A systematic approach to evaluation can guide a more targeted approach to genetic evaluation, diagnosis, and management of NIHF.

Lysosomal storage disorder in non-immunological hydrops fetalis (NIHF): more common than assumed? Report of four cases with transient NIHF and a review of the literature

Background

Lysosomal storage disorders (LSD) are a rare cause of non immunological hydrops fetalis (NIHF) and congenital ascites. The reported incidence is about 1%. The incidence of idiopathic NIHF is estimated to be about 18%.

Patients and methods

We report four cases with transient hydrops fetalis resulting from LSD and performed a literature review on LSD with NIHF and congenital ascites in combination.

Results

At present, 12 different LSDs are described to be associated with NIHF or congenital ascites. Most patients had a family history of NIHF, where the preceding sibling had not been examined. A diagnostic approach to the fetus with NIHF due to suspected LSD either in utero or postnatal is suggested. Transient forms of NIHF and/or ascites in association with MPS IVA, MPS VII and NPC are described for the first time in this publication.

Conclusions

LSD should be considered in transient hydrops. Enzymatic studies in chorionic villous sample or amniotic cultured cells, once the most common conditions associated with fetal ascites or hydrops have been ruled out, are important. This paper emphasizes the fact that LSD is significantly higher than the estimated 1% in previous studies, which is important for genetic counseling as there is a high risk of recurrence and the availability of enzyme replacement therapy for an increasing number of LSD.

Adverse pregnancy outcomes after abnormal first-trimester screening for aneuploidy

Women with abnormal results of first trimester screening but with a normal karyotype are at risk for adverse pregnancy outcomes. A nuchal translucency of greater than 3.5 mm is associated with an increased risk of subsequent pregnancy loss, fetal infection, fetal heart abnormalities, and other structural abnormalities. Abnormal levels of first trimester analytes are also associated with adverse pregnancy outcomes, but the predictive value is less impressive. As a single marker, pregnancy-associated plasma protein (PAPP)-A level less than 1st percentile has a good predictive value for subsequent fetal growth restriction. Women with PAPP-A level less than 5th percentile should undergo subsequent risk assessment with routine maternal serum afetoprotein screening with the possible addition of uterine artery pulsatility index assessment in the midtrimester.

Lysosomal storage disorders in the newborn

Lysosomal storage disorders are rare inborn errors of metabolism, with a combined incidence of 1 in 1500 to 7000 live births. These relatively rare disorders are seldom considered when evaluating a sick newborn. A significant number of the >50 different lysosomal storage disorders, however, do manifest in the neonatal period and should be part of the differential diagnosis of several perinatal phenotypes. We review the earliest clinical features, diagnostic tests, and treatment options for lysosomal storage disorders that can present in the newborn. Although many of the lysosomal storage disorders are characterized by a range in phenotypes, the focus of this review is on the specific symptoms and clinical findings that present in the perinatal period, including neurologic, respiratory, endocrine, and cardiovascular manifestations, dysmorphic features, hepatosplenomegaly, skin or ocular involvement, and hydrops fetalis/congenital ascites. A greater awareness of these features may help to reduce misdiagnosis and promote the early detection of lysosomal storage disorders. Implementing therapy at the earliest stage possible is crucial for several of the lysosomal storage disorders; hence, an early appreciation of these disorders by physicians who treat newborns is essential.

Recurrent Fetal Hydrops due to Mucopolysaccharidoses Type VII

Hydrops fetalis is associated with a wide range of abnormalities. In about 20% of cases of non-immune fetal hydrops, no cause is found despite investigations including routine post-mortem examination and enzyme studies may be indicated to detect an underlying metabolic storage disease. Fetal hydrops due to mucopolysaccharidosis type VII is very rare and a prenatal diagnosis is not usually made. We report a case of mucopolysaccharidosis type VII presenting as recurrent fetal hydrops and review the clinico-pathological features of this disorder.

Increased nuchal translucency with normal karyotype

Increased fetal nuchal translucency (NT) thickness between 11 and 14 weeks' gestation is a common phenotypic expression of chromosomal abnormalities, including trisomy 21. However, even in the absence of aneuploidy, nuchal thickening is clinically relevant because it is associated with an increase in adverse perinatal outcome caused by a variety of fetal malformations, dysplasias, deformations, dysruptions, and genetic syndromes. Once the presence of aneuploidy is ruled out, the risk of perinatal outcome dose not statistically increase until the nuchal translucency measurement reaches 3.5 mm or more (>99th percentile). This increase in risk occurs in an exponential fashion as the NT measurement increases. However, if the fetus survives until midgestation, and if a targeted ultrasound at 20 to 22 weeks fails to reveal any abnormalities, the risk of an adverse perinatal outcome and postnatal developmental delay is not statistically increased.

First-trimester fetal nuchal translucency and inherited metabolic disorders

OBJECTIVES

To assess the association between inherited metabolic disorders and nuchal translucency (NT) measurements.

METHODS

The NT measurements obtained from 66 fetuses at high risk for metabolic diseases prior to chorionic villus sampling (CVS) were retrospectively analysed.

RESULTS

NT was found to be within the normal range in all of the 13 affected fetuses, which included three with Gaucher disease, two with glycogenosis type II, two with mucopolysaccharidosis type I and six others with Krabbe disease, metachromatic leukodystrophy, mucopolysaccharidosis type II, Niemann-Pick A disease, Pelizaeus-Merzbacher disease and sialidosis, respectively. An increased nuchal thickness was found only in one fetus affected with trisomy 21 but not affected with mucopolysaccharidosis type II.

CONCLUSION

NT appears to have a limited role in identifying affected fetuses in pregnancies at high risk for inherited metabolic disorders. NT may be normal in early pregnancy even for fetuses affected with conditions known to be associated with non-immune hydrops fetalis.

Mucopolysaccharidosis type VII as a cause of recurrent non-immune hydrops fetalis

BACKGROUND

Mucopolysaccharidosis type VII (MPS VII) is a rare lysosomal storage disease first described by Sly in 1973. There are fewer than thirty reported cases world wide. This extremely rare disorder can present in-utero as hydrops fetalis and has a high recurrence rate. However, prenatal diagnosis in the absence of a previously affected child, has not been reported to date.

CASE

This is a case of a non-consanguineous couple, with no history of a previously affected child with MPS VII, presenting with recurrent hydrops fetalis. During the work-up, the affected fetus was diagnosed in-utero with beta-glucuronidase deficiency which is pathognomonic for MPS VII. Prenatal diagnosis was then performed in subsequent pregnancies.

CONCLUSION

The importance of an extensive and thorough investigation for the etiology of hydrops fetalis is discussed.

Outcome of fetuses with increased nuchal translucency

Recent reports on nuchal translucency screening in unselected patient populations show results that are comparable with those reported by the thus far largest series on screening for Down's syndrome based on maternal age and nuchal translucency measurement. Much interest is focused on the prognostic value of increased nuchal translucency in fetuses with normal chromosomes. Increased nuchal translucency is regarded as a clear sign of declining fetal health, which can be associated with fetal demise, structural anomalies, rare genetic syndromes, and in particular congenital heart defects. A clear association is demonstrated between nuchal translucency above the 99th centile and congenital cardiac defects. Such a finding should prompt specialized echocardiography. However, on the whole the sensitivity of nuchal translucency screening is too low to consider this as the sole criterion to screen for critical heart defects.