👤 Aya Shibamiya

IgM-related AL amyloidosis is a rare and distinct clinical entity, often associated with underlying lymphoproliferative disorders such as Waldenström's macroglobulinemia (WM) or lymphoplasmacytic lymphoma (LPL). Unlike non-IgM AL amyloidosis, it exhibits unique organ involvement patterns and generally poorer prognosis. We report a 66-year-old woman diagnosed with WM complicated by systemic IgM-κ AL amyloidosis. She received combination chemotherapy with rituximab and bendamustine (BR), resulting in a reduction of serum IgM levels. Despite the hematologic improvement, her liver dysfunction rapidly progressed, and she died of hepatic failure just two months after diagnosis. Pathological autopsy revealed massive IgM-κ amyloid deposition in the liver and multiple organs, with no residual lymphoma in the bone marrow or lymph nodes. These findings suggest that extensive hepatic amyloid infiltration was already present at diagnosis, and that organ response could not be achieved despite hematologic improvement. This case highlights the aggressive nature of IgM-related AL amyloidosis and the critical importance of early detection, especially when liver dysfunction is observed. Current therapies targeting the underlying clone may not be sufficient in cases with advanced organ involvement, emphasizing the urgent need for novel strategies to facilitate amyloid clearance and protect organ function. Show less

MYBPC3 is the most frequently affected gene in hypertrophic cardiomyopathy (HCM), which is an autosomal-dominant cardiac disease caused by mutations in sarcomeric proteins. Bi-allelic truncating MYBPC3 mutations are associated with severe forms of neonatal cardiomyopathy. We reprogrammed skin fibroblasts from a HCM patient carrying a heterozygous MYBPC3 truncating mutation into human induced pluripotent stem cells (iPSC) and used CRISPR/Cas9 to generate bi-allelic MYBPC3 truncating mutation and isogenic control hiPSC lines. All lines expressed pluripotency markers, had normal karyotype and differentiated into endoderm, ectoderm and cardiomyocytes in vitro. This set of three lines provides a useful tool to study HCM pathomechanisms. Show less

Gene therapy is a promising option for severe forms of genetic diseases. We previously provided evidence for the feasibility of trans-splicing, exon skipping, and gene replacement in a mouse model of hypertrophic cardiomyopathy (HCM) carrying a mutation in MYBPC3, encoding cardiac myosin-binding protein C (cMyBP-C). Here we used human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from an HCM patient carrying a heterozygous c.1358-1359insC MYBPC3 mutation and from a healthy donor. HCM hiPSC-CMs exhibited ∼50% lower MYBPC3 mRNA and cMyBP-C protein levels than control, no truncated cMyBP-C, larger cell size, and altered gene expression, thus reproducing human HCM features. We evaluated RNA trans-splicing and gene replacement after transducing hiPSC-CMs with adeno-associated virus. trans-splicing with 5' or 3' pre-trans-splicing molecules represented ∼1% of total MYBPC3 transcripts in healthy hiPSC-CMs. In contrast, gene replacement with the full-length MYBPC3 cDNA resulted in ∼2.5-fold higher MYBPC3 mRNA levels in HCM and control hiPSC-CMs. This restored the cMyBP-C level to 81% of the control level, suppressed hypertrophy, and partially restored gene expression to control level in HCM cells. This study provides evidence for (1) the feasibility of trans-splicing, although with low efficiency, and (2) efficient gene replacement in hiPSC-CMs with a MYBPC3 mutation. Show less