MYH11-Related Hereditary Type 2 Visceral Myopathy in a Large Kindred: Diagnostic Odyssey With Milder Clinical Manifestations.

MYH11-related hereditary type 2 visceral myopathy is a rare smooth muscle disorder typically presenting in infancy with severe gastrointestinal and genitourinary dysfunction. We describe a 73-year-old female with lifelong symptoms of gastrointestinal and urinary dysfunction, including chronic constipation, neurogenic bladder, recurrent urinary tract infections, gastroparesis, and pelvic organ prolapse. A multigenerational family history revealed similar visceral smooth muscle abnormalities among 14 affected individuals over five generations, suggesting autosomal dominant inheritance. Whole-genome sequencing identified a heterozygous, likely pathogenic variant in MYH11 c.5819del; p.(Pro1940HisfsTer91), consistent with the diagnosis of autosomal dominant type 2 visceral myopathy. This variant causes production of an abnormally elongated myosin-heavy chain, disrupting muscle contractile function. This individual's survival into her eighth decade reflects long-term clinical stability, possibly attributable to the variant's milder effect. We describe the clinical course of the disease, along with a comprehensive review of previously described individuals with the same variant. This case broadens the phenotypic spectrum of MYH11-associated visceral myopathy, demonstrating that late-onset, milder forms can occur and remain compatible with long-term survival with optimal supportive management. Comprehensive genetic evaluation identifies primary disorders, enabling precise diagnosis, tailored management, and informed genetic counseling for complex phenotypes.