Variant in ACTG2 Causing Megacystis Microcolon Hypoperistalsis Syndrome and Severe Familial Postpartum Bleeding.

INTRODUCTION: Megacystis microcolon hypoperistalsis syndrome (MMIHS) is a rare condition with high morbidity and mortality. It is characterized by megacystis, microcolon, and intestinal hypoperistalsis leading to various grades of bladder and bowel obstruction. CASE PRESENTATION: This report describes a pregnant woman with a history of bowel obstruction, urine retention, and heavy postpartum bleeding where ultrasound findings of fetal megacystis during pregnancy led to genetic testing in the family. The fetus, the pregnant woman, and four female family members were heterozygous for a pathogenic variant detected in the ACTG2 gene. The fetus was treated successfully for hydronephrosis using vesicoamniotic shunting. DISCUSSION: Early diagnosis of a fetus with MMIHS is important to secure multidisciplinary prenatal and neonatal treatment. Furthermore, gene testing must be considered when a woman presents a history of pseudo-obstruction and urine retention to prevent complications during pregnancy and labor. Finally, recurrent familial postpartum bleeding should lead to referral to genetic evaluation.

Clinical characterisation of the multiple maternal hypomethylation syndrome in siblings.

We present the first clinical report of sibs with the multiple maternal hypomethylation syndrome. Both sisters presented with transient neonatal diabetes mellitus (TNDM). By methylation-specific PCR of bisulphite-treated DNA, we found a mosaic spectrum of hypomethylation at the following maternally methylated loci in both sibs: ZAC (6q24), KCNQ1OT1 (11p15.5), GRB10 (7p11.2-12), PEG3 (19q13), PEG1/MEST (7q32), and NESPAS (20q13). While the older sister has a milder phenotype, the younger one was severely ill and died at 11 months of age. Despite phenotypic differences, the sisters had several manifestations of both TNDM and BWS in common. The family is highly consanguineous, and the parents are first cousins. We suggest that the genetic defect in this family is a novel, most likely autosomal recessive defect of methylation mechanisms, either in the sisters or in their mother, affecting her oocyte imprinting. The recurrence with affected sibs as reported in this family has implications for genetic counselling.

Hypomethylation of multiple imprinted loci in individuals with transient neonatal diabetes is associated with mutations in ZFP57.

We have previously described individuals presenting with transient neonatal diabetes and showing a variable pattern of DNA hypomethylation at imprinted loci throughout the genome. We now report mutations in ZFP57, which encodes a zinc-finger transcription factor expressed in early development, in seven pedigrees with a shared pattern of mosaic hypomethylation and a conserved range of clinical features. This is the first description of a heritable global imprinting disorder that is compatible with life.