Paraneoplastic Autoimmune Multiorgan Syndrome: Diagnostic Lessons for Pediatricians

We report the challenging diagnosis of an 11-year-old boy, presenting with subacute erythroblastopenia, followed by a multisystemic immune-mediated syndrome characterized by polymorphic mucocutaneous manifestations, associated with severe myositis related to a dermatomyositis-like phenotype and mild hepatitis. A progressive lymphadenopathy led to a delayed diagnosis of T-lymphoblastic lymphoma associated with paraneoplastic autoimmune multiorgan syndrome. To achieve remission of this paraneoplastic syndrome, Janus kinase inhibitor was required in addition to antitumor therapy. This case highlights several key points: (1) Pediatricians should consider a paraneoplastic origin when facing juvenile dermatomyositis with atypical features, such as hematologic and mucosal abnormalities; (2) in uncertain cases, early collaboration with oncologists is needed to optimize diagnostic and therapeutic strategies; (3) the choice of immunomodulatory therapy is critical in addition to antitumor therapy.