Clinical and genetic analysis of a family with 16p11.2 microduplication syndrome and variable multisystem...

16p11.2 microduplication syndrome (OMIM #614671) is a pathogenic recurrent copy-number gain at the 16p11.2 locus and is associated with variable expressivity across neurodevelopmental, growth, and medical phenotypes. Gastrointestinal symptoms have been reported in carrier cohorts, but detailed documentation of gastrointestinal motility and neuromuscular findings remains limited. We performed clinical and genetic analyses in a multigenerational family in which the proband (III1) presented with limb muscle pain, exercise intolerance, and chronic gastrointestinal symptoms. Next-generation sequencing (NGS), low-pass whole-genome sequencing (lpWGS)-based CNV analysis, Sanger sequencing, and qPCR validation identified a 0.8 Mb microduplication at 16p11.2 (BP4-BP5), involving 44 genes including TBX6, inherited from the mother (II2). The proband's clinical manifestations included developmental delay, pointed chin, low body mass index, gastrointestinal dysfunction (chronic abdominal pain, diarrhea, esophageal motility disorder, and rectal prolapse), forward-leaning gait, mild scoliosis, and limb muscle atrophy with inflammatory muscle involvement. Four family members (II2, III1, III2, and III4) carried the microduplication, but their available clinical features varied in severity and system involvement. The proband's twin brother (III2) had left ear deafness and epilepsy, individual II2 had blindness from cone-rod dystrophy, and III4 showed more pronounced scoliosis. This family provides a detailed clinical and genetic description of 16p11.2 microduplication carriers with prominent gastrointestinal motility and neuromuscular manifestations, thereby enriching the clinical characterization of this recurrent CNV and supporting substantial intrafamilial phenotypic heterogeneity.