Expanding the genotypic spectrum of ACTG2-related visceral myopathy.

Visceral myopathies (VMs) encompass a spectrum of disorders characterized by chronic disruption of gastrointestinal function, with or without urinary system involvement. Pathogenic missense variation in smooth muscle gamma-actin gene (ACTG2) is associated with autosomal dominant VM. Whole genome sequencing of an infant presenting with chronic intestinal pseudo-obstruction revealed a homozygous 187 base pair (c.589_613+163del188) deletion spanning the exon 6-intron 6 boundary within ACTG2. The patient's clinical course was marked by prolonged hospitalizations, multiple surgeries, and intermittent total parenteral nutrition dependence. This case supports the emerging understanding of allelic heterogeneity in ACTG2-related VM, in which both homozygous and heterozygous variants in ACTG2 are associated with gastrointestinal dysfunction of similar severity and overlapped clinical presentation. Moreover, it illustrates the clinical utility of rapid whole genome sequencing, which can comprehensively and precisely detect different types of genomic variants including small deletions, leading to guidance of clinical care decisions.