Case Report: First occurrence of smoldering multiple myeloma in activated phosphoinositide 3-Kinase δ syndrome

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Activated phosphoinositide 3-kinase δ syndrome (APDS) is an inborn error of immunity caused by mutations in PIK3CD or PIK3R1.
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The report describes a young patient with recurrent infections and smoldering multiple myeloma (SMM) associated with a PIK3CD mutation.
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Smoldering multiple myeloma is a pre-malignant condition that can progress to symptomatic multiple myeloma over time.
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The patient exhibited elevated serum IgM and IgG levels, lymphoproliferation, and a history of autoimmune conditions.
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This case highlights the potential link between PI3K signaling dysregulation and plasma cell disorders, expanding the tumor spectrum of APDS.

Frontiers In Oncology

by Yanqiu Li, Linlin Huang, Wenhua He, Xin Wang, Ningning Tang, Dongmei Zhu, Xingli Jia, Chao Ding
June 11, 2026

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