Prenatal presentation of Walker–Warburg syndrome with a POMT2 mutation: an extended fetal phenotype

Cobblestone lissencephaly (Type II), clinical, and neuroimaging: A case report and literature review

Cobblestone lissencephaly (C-LIS) (TYPE II) is a rare and severe neuronal migration disorder characterized by a smooth brain surface with overmigrated neurons and abnormal formation of cerebral convolutions or gyri during fetal development, resulting in a cobblestone appearance. C-LIS is associated with eye anomalies and muscular dystrophy. This case report presents a detailed clinical and neuroimaging analysis of a patient diagnosed with cobblestone lissencephaly (Type II). It reviews pertinent literature to enhance our understanding of this complex condition. We report a case of a 6-year-old female child with cobblestone lissencephaly (C-LIS) (Type II) severe developmental delays, hypotonia, and recurrent intractable seizures. Magnetic resonance imaging (MRI) revealed a characteristic cobblestone appearance on the brain surface, indicative of abnormal neuronal migration. In addition to the classic findings of Type II Cobblestone lissencephaly, the patient displayed ventriculomegaly and cerebellar hypoplasia, contributing to the overall neurological impairment observed. The literature review highlights the genetic basis of cobblestone lissencephaly, emphasizing the involvement of genes associated with glycosylation processes and basement membrane integrity. Neuroimaging findings, including MRI and computed tomography scans, are crucial for accurate diagnosis and prognostication. Early identification of cobblestone lissencephaly allows for appropriate counseling and management strategies. However, the prognosis remains guarded, and interventions primarily focus on supportive care and seizure management. This case report contributes to the knowledge of cobblestone lissencephaly, shedding light on the clinical spectrum and neuroimaging features associated with this rare disorder. To clarify the underlying genetic mechanisms and possible therapeutic pathways for better patient outcomes, more investigation is necessary.

Fetal Presentation of Walker-Warburg Syndrome with Compound Heterozygous POMT2 Missense Mutations

Background: Walker-Warburg syndrome (WWS) (OMIM #236670) is an autosomal recessive disorder characterized by congenital muscular dystrophy, hydrocephalus, cobblestone lissencephaly, and retinal dysplasia. The main genes involved are: POMT1, POMT2, POMGNT1, FKTN, LARGE1, and FKRP. Case report: We present a fetus with WWS showing at ultrasound severe triventricular hydrocephalus. Pregnancy was legally terminated at 21 weeks +2 days of gestation. In vivo and postmortem magnetic resonance revealed corpus callosum agenesis and cerebellar hypoplasia. Cobblestone lissencephaly was observed at post-mortem. Next generation sequencing (NGS) of 193 genes, performed on fetal DNA extracted from amniocytes, detected two heterozygous mutations in the POMT2 gene. The c.1238G > C p.(Arg413Pro) mutation was paternally inherited and is known to be pathogenic. The c.553G > A p.(Gly185Arg) mutation was maternally inherited and has not been previously described. Conclusion: Compound heterozygous mutations in the POMT2 gene caused a severe cerebral fetal phenotype diagnosed prenatally at midgestation allowing therapeutic pregnancy termination.

Congenital hydrocephalus: new Mendelian mutations and evidence for oligogenic inheritance

BACKGROUND

Congenital hydrocephalus is characterized by ventriculomegaly, defined as a dilatation of cerebral ventricles, and thought to be due to impaired cerebrospinal fluid (CSF) homeostasis. Primary congenital hydrocephalus is a subset of cases with prenatal onset and absence of another primary cause, e.g., brain hemorrhage. Published series report a Mendelian cause in only a minority of cases. In this study, we analyzed exome data of PCH patients in search of novel causal genes and addressed the possibility of an underlying oligogenic mode of inheritance for PCH.

MATERIALS AND METHODS

We sequenced the exome in 28 unrelated probands with PCH, 12 of whom from families with at least two affected siblings and 9 of whom consanguineous, thereby increasing the contribution of genetic causes. Patient exome data were first analyzed for rare (MAF < 0.005) transmitted or de novo variants. Population stratification of unrelated PCH patients and controls was determined by principle component analysis, and outliers identified using Mahalanobis distance 5% as cutoff. Patient and control exome data for genes biologically related to cilia (SYScilia database) were analyzed by mutation burden test.

RESULTS

In 18% of probands, we identify a causal (pathogenic or likely pathogenic) variant of a known hydrocephalus gene, including genes for postnatal, syndromic hydrocephalus, not previously reported in isolated PCH. In a further 11%, we identify mutations in novel candidate genes. Through mutation burden tests, we demonstrate a significant burden of genetic variants in genes coding for proteins of the primary cilium in PCH patients compared to controls.

CONCLUSION

Our study confirms the low contribution of Mendelian mutations in PCH and reports PCH as a phenotypic presentation of some known genes known for syndromic, postnatal hydrocephalus. Furthermore, this study identifies novel Mendelian candidate genes, and provides evidence for oligogenic inheritance implicating primary cilia in PCH.