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E-Poster Submission Deadline
Please prepare and upload your E-Poster no later than March 14, 2026 11.59PM CET. After this date, you will no longer be able to prepare and upload your E-poster and it will not be displayed and accessible on the congress website.
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Abstract titles should be brief and reflect the content of the abstract.
CBL syndrome, caused by germline mutations in the CBL gene, is classified as a RASopathy and is characterized by Noonan-like features, juvenile myelomonocytic leukemia (JMML) predisposition, autoimmunity, and developmental delay. Although abnormalities in the RAS/MAPK pathway underlie the pathogenesis of RASopathies, reports of immune-mediated kidney disease associated with RASopathies are rare, and its mechanisms remain unclear. Here we report a pediatric case of CBL syndrome complicated by steroid-resistant nephrotic syndrome (SRNS), in whom circulating anti-nephrin antibodies were detected.
We present a pediatric case of CBL syndrome with anti-nephrin antibody positive nephrotic syndrome.
A boy was referred to our hospital at 5 months of age with thrombocytopenia and anemia. The diagnosis of Evans syndrome was made together with hepatosplenomegaly, initially raising suspicion for autoimmune lymphoproliferative syndrome (ALPS). Genetic testing excluded ALPS-related mutations but identified a known heterozygous missense mutation in CBL gene (c.1111T>C), leading to a diagnosis of CBL syndrome. At 2 years old, he developed nephrotic syndrome. Despite standard therapy with glucocorticoid (GC) based on The International Study of Kidney Disease in Children (ISKDC) protocol, he exhibited a GC resistant course. Renal biopsy showed minimal change without immune complex deposition with diffuse podocyte foot process effacement on electron microscopy, consistent with podocytopathy. Remission of nephrotic syndrome was not achieved despite additional treatment with methylprednisolone pulse therapy, mycophenolate mofetil, and cyclosporine A. Rituximab (RTX) was initiated subsequently, which resulted in complete remission. GCs and immunosuppressive agents were successfully discontinued. Disease relapse coincided with B cell reconstitution but was again controlled by RTX re-administration for more than two years. Importantly, plasma testing revealed positivity for anti-nephrin antibodies, suggesting an autoimmune podocytopathy.
This is the first reported case of CBL syndrome complicated by nephrotic syndrome with anti-nephrin antibody positivity. The clinical course, including RTX responsiveness, suggests that dysregulated B cell function and autoantibody production may play a central role in disease pathogenesis. These findings expand the clinical spectrum of RASopathy including CBL syndrome, highlighting a potential mechanistic link between RAS/MAPK pathway, B cell dysregulation and autoimmunity.
