Immunoglobulin light chain (AL) amyloidosis and POEMS syndrome are plasma cell proliferative disorders involving multiple organs and tissues, often presenting with nonspecific clinical manifestations. The co-occurrence of both conditions in a single patient is clinically rare and can easily lead to misdiagnosis or underdiagnosis. This report describes an elderly male patient who presented primarily with refractory heart failure and was ultimately diagnosed with coexisting AL amyloidosis and POEMS syndrome. The patient received 12 cycles of treatment with bortezomib, cyclophosphamide, and dexamethasone (BCD), achieving significant clinical and biochemical remission. This case underscores that while the coexistence of rare diseases is uncommon, it represents an important cause of clinical complexity and treatment resistance. A comprehensive etiological diagnosis is therefore a crucial prerequisite for formulating an effective and individualized treatment plan.
