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Homozygous Phosphatidylinositol Glycan Class T Mutation in an Indian Girl With Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome 3.

ABSTRACT: Multiple congenital anomalies-hypotonia-seizures syndrome 3 (MCAHS3) is a rare genetic disorder, characterized by infantile-onset epilepsy, hypotonia, global developmental delay, dysmorphic features, and variable congenital anomalies involving the cardiac, skeletal, and genitourinary systems. It is caused by the homozygous or compound heterozygous mutation in the phosphatidylinositol glycan class T (PIGT) gene. Only fewer cases were reported in the literature till now. We described a PIGT mutation in an Indian girl with global developmental delay, infantile-onset seizures, hypotonia, and facial dysmorphism. This case will help to expand the clinical spectrum of PIGT mutation.

SUBMITTER: Sai Chandar D

PROVIDER: S-EPMC8163346 | biostudies-literature | 2021 Apr

REPOSITORIES: biostudies-literature

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Homozygous Phosphatidylinositol Glycan Class T Mutation in an Indian Girl With Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome 3.

Sai Chandar Dudipala D Krishna Chaithanya Battu B Prashanthi Mandapuram M

Cureus 20210428 4

Multiple congenital anomalies-hypotonia-seizures syndrome 3 (MCAHS3) is a rare genetic disorder, characterized by infantile-onset epilepsy, hypotonia, global developmental delay, dysmorphic features, and variable congenital anomalies involving the cardiac, skeletal, and genitourinary systems. It is caused by the homozygous or compound heterozygous mutation in the phosphatidylinositol glycan class T (PIGT) gene. Only fewer cases were reported in the literature till now. We described a PIGT mutati ...[more]

PMID: 34084664

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Project description:ObjectiveTo summarize and extend the phenotypic characterization of Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome, and to discuss genotype-phenotype correlations.MethodsCollecting clinical information of 17 patients with pathogenic variants in PIGN, PIGA, and PIGT. Genetic studies were performed on all patients.ResultsThere were 7 patients with 15 PIGN mutations (one patient carrying 3 mutations), 8 patients with 8 PIGA mutations, and 2 patients with 5 PIGT mutations (one patient carrying 3 mutations). All patients had epilepsy and developmental delay, with 71% of them showed hypotonia. And among these patients' various seizure types, the focal seizure was the most common one. Eighty-two percent patients showed a significant relationship between seizures and fever. Serum ALP was elevated in one patient with PIGN mutations and in two patients with PIGA mutations. Brain MRI showed enlarged subarachnoid space in 56% of patients. Some other different characteristics had also been found in our patients: First, atypical absence seizures presented in three patients with PIGN mutations; Second, diffuse slow waves mixed with focal or multifocal discharges of interictal EEG in 88% cases with PIGA-deficient; Third, phenotypes of seven out of eight patients with PIGA mutations were difficult to be classified as severe or less severe group; Last, mild neurological symptoms and developmental status rather than severe conditions occurred in one patient with PIGT mutations.ConclusionWith epilepsy, developmental delay, and/or hypotonia as common features, the knowledge of MCAHS in terms of phenotype and genotype has been expanded. In cases with PIGN-deficient, we expanded the types of atypical absence seizures, and described one patient with elevated serum ALP. Focal seizures with diffuse slow waves mixed with focal or multifocal discharges on EEG rather than infantile spasms with hypsarrhythmia, which as previously reported were often seen in our patients with PIGA mutations. The classifications of phenotypes caused by PIGA mutations should be more continuous than discrete. The mild phenotype of one patient with PIGT mutations expanded the clinical presentation of MCAHS3.

Project description:PurposeBiallelic PIGN variants have been described in Fryns syndrome, multiple congenital anomalies-hypotonia-seizure syndrome (MCAHS), and neurologic phenotypes. The full spectrum of clinical manifestations in relation to the genotypes is yet to be reported.MethodsGenotype and phenotype data were collated and analyzed for 61 biallelic PIGN cases: 21 new and 40 previously published cases. Functional analysis was performed for 2 recurrent variants (c.2679C>G p.Ser893Arg and c.932T>G p.Leu311Trp).ResultsBiallelic-truncating variants were detected in 16 patients-10 with Fryns syndrome, 1 with MCAHS1, 2 with Fryns syndrome/MCAHS1, and 3 with neurologic phenotype. There was an increased risk of prenatal or neonatal death within this group (6 deaths were in utero or within 2 months of life; 6 pregnancies were terminated). Incidence of polyhydramnios, congenital anomalies (eg, diaphragmatic hernia), and dysmorphism was significantly increased. Biallelic missense or mixed genotype were reported in the remaining 45 cases-32 showed a neurologic phenotype and 12 had MCAHS1. No cases of diaphragmatic hernia or abdominal wall defects were seen in this group except patient 1 in which we found the missense variant p.Ser893Arg to result in functionally null alleles, suggesting the possibility of an undescribed functionally important region in the final exon. For all genotypes, there was complete penetrance for developmental delay and near-complete penetrance for seizures and hypotonia in patients surviving the neonatal period.ConclusionWe have expanded the described spectrum of phenotypes and natural history associated with biallelic PIGN variants. Our study shows that biallelic-truncating variants usually result in the more severe Fryns syndrome phenotype, but neurologic problems, such as developmental delay, seizures, and hypotonia, present across all genotypes. Functional analysis should be considered when the genotypes do not correlate with the predicted phenotype because there may be other functionally important regions in PIGN that are yet to be discovered.

Project description:BackgroundGlycosylphosphatidylinositol (GPI) anchoring is a special type of protein posttranslational modification, by which proteins with diverse function are attached to cell membrane through a covalent linkage between the protein and the glycolipid. Phosphatidylinositol glycan anchor biosynthesis class A (PIGA) is a key enzyme in GPI anchor biosynthesis, somatic mutations or genetic variants of which have been associated with paroxysmal nocturnal hemoglobinuria (PNH), or PIGA deficiency, respectively. More than 10 PIGA pathogenic or likely pathogenic variants have been reported in a wide spectrum of clinical syndromes of PIGA deficiency, including multiple congenital anomalies hypotonia-seizures syndrome 2 (MCAHS2).MethodsWhole-exome sequencing (WES) was performed on two trios, that is., the proband's family and his affected maternal cousin's family, from a nonconsanguineous Chinese family pedigree with hypotonia-encephalopathy-seizures disease history and putative X-linked recessive inheritance. Sanger sequencing for PIGA variant was performed on affected members as well as unaffected members in the family pedigree to verify its familial segregation.ResultsA novel likely pathogenic variant in PIGA was identified through comparative WES analysis of the two affected families. The single-nucleotide substitution (NC_000023.9:g.15343279T>C) is located in intron 3 of the PIGA gene and within the splice acceptor consensus sequence (NM_002641.3:c.849-5A>G). Even though we have not performed RNA studies, in silico tools predict that this intronic variant may alter normal splicing, causing a four base pair insertion which creates a frameshift and a premature stop codon at position 297 (NP_002632.1:p.(Arg283Serfs*15)). Sanger sequencing analysis of the extended family members confirmed the presence of the variant and its X-linked inheritance.ConclusionWES data analysis along with familial segregation of a rare intronic variant are suggestive of a diagnosis of X-liked PIGA deficiency with clinical features of MCAHS2.

Dataset Information

Homozygous Phosphatidylinositol Glycan Class T Mutation in an Indian Girl With Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome 3.

Publications

Homozygous Phosphatidylinositol Glycan Class T Mutation in an Indian Girl With Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome 3.

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