👤 Martin B Delatycki

Periventricular nodular heterotopia (PVNH) is a common malformation of cortical development. We describe a distinctive imaging phenotype characterized by bilateral small heterotopic nodules of grey matter in the frontal periventricular regions, with an overview of the clinical, imaging, and genetic features. Investigators reviewed available brain MRI studies, clinical records and genetic findings of 32 individuals with bilateral frontal PVNH, ascertained from multiple centres between 1996 and 2021. The imaging phenotype consists of multiple, small, bilateral nodules of PVNH maximal along the frontal horns of the lateral ventricles. Frontal PVNH was associated with heterogeneous, often subtle, additional brain malformations in 72 % (23/32) individuals. The clinical phenotype was variable and included mild focal epilepsy in 7/32 and mild-moderate cognitive impairment or developmental delay in 13/32. Microarray was normal in 13/16 and exome or genome sequencing normal in 8/13 where testing was performed. A genetic diagnosis was achieved in seven patients; pathogenic chromosome deletions of 7q11.23 and 7p22.1, pathogenic intragenic variants in KANSL1, STXBP1 and MAP1B (mother-daughter pair), and a combined 13q12.12 deletion (containing SACS) and an intragenic SACS variant. Bilateral frontal PVNH has a variable clinical phenotype, but generally milder sequelae than other forms of bilateral PVNH. A genetic diagnosis was made by chromosome microarray alone in 13 % or by exome or genome sequencing in 38 % where access to testing was available, with no recurrent genetic cause being found. Our PVNH cohort data suggest that PVNH could be classified in three main groups: FLNA-associated "classic" bilateral frontocentral PVNH, posterior/infrasylvian PVNH and this third pattern of bilateral frontal PVNH, accounting for ∼10 % of all cases of PVNH. Show less

Primary chronic intestinal pseudo-obstruction (CIPO) is a rare, potentially life-threatening disorder characterized by severely impaired gastrointestinal motility. The objective of this study was to examine the contribution of ACTG2, LMOD1, MYH11, and MYLK mutations in an Australasian cohort of patients with a diagnosis of primary CIPO associated with visceral myopathy. Pediatric and adult patients with primary CIPO and suspected visceral myopathy were recruited from across Australia and New Zealand. Sanger sequencing of the genes encoding enteric gamma-actin (ACTG2) and smooth muscle leiomodin (LMOD1) was performed on DNA from patients, and their relatives, where available. MYH11 and MYLK were screened by next-generation sequencing. We identified heterozygous missense variants in ACTG2 in 7 of 17 families (~41%) diagnosed with CIPO and its associated conditions. We also identified a previously unpublished missense mutation (c.443C>T, p.Arg148Leu) in one family. One case presented with megacystis-microcolon-intestinal hypoperistalsis syndrome in utero with subsequent termination of pregnancy at 28 weeks' gestation. All of the substitutions identified occurred at arginine residues. No likely pathogenic variants in LMOD1, MYH11, or MYLK were identified within our cohort. ACTG2 mutations represent a significant underlying cause of primary CIPO with visceral myopathy and associated phenotypes in Australasian patients. Thus, ACTG2 sequencing should be considered in cases presenting with hypoperistalsis phenotypes with suspected visceral myopathy. It is likely that variants in other genes encoding enteric smooth muscle contractile proteins will contribute further to the genetic heterogeneity of hypoperistalsis phenotypes. Show less