IgD-λ POEMS syndrome presenting with edema, pulmonary hypertension, and renal impairment: A case report

RATIONALE: Polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma-cell disorder, and skin changes (POEMS) syndrome is a rare multisystem syndrome associated with clonal plasma-cell disorders. The IgD-λ subtype is uncommon, and a low-level monoclonal protein may escape detection by routine electrophoresis and immunofixation electrophoresis (IFE), delaying diagnosis. PATIENT CONCERNS: A 38-year-old woman was admitted in April 2025 with intermittent bilateral lower-extremity edema for >3 years, elevated serum creatinine for 8 months, and acute worsening over 4 days. She subsequently developed pulmonary hypertension, polyserous effusions, splenomegaly, lymphadenopathy, anemia, thrombocytosis, and renal impairment, and had been diagnosed elsewhere with idiopathic pulmonary arterial hypertension. DIAGNOSES: Right-heart catheterization confirmed precapillary pulmonary hypertension. Routine serum and urine protein studies, including IFE, were negative. Following multidisciplinary evaluation, nerve-conduction studies showed peripheral neuropathy; serum vascular endothelial growth factor (VEGF) was elevated; and bone marrow studies demonstrated a clonal plasma-cell population with cytoplasmic λ light-chain restriction. Extended serum IFE, including anti-IgD and anti-IgE antisera, detected a trace, nonquantifiable monoclonal IgD component, establishing IgD-λ POEMS syndrome. Renal biopsy showed POEMS-associated glomerular microangiopathy-like lesions with acute tubular injury. INTERVENTIONS: The patient received dexamethasone acetate plus lenalidomide and underwent autologous stem-cell transplantation on December 2, 2025. OUTCOMES: By March 2026, peripheral edema had resolved, pulmonary hypertension was mild on echocardiography, serum creatinine had decreased to 60 μmol/L, and VEGF had normalized. LESSONS: POEMS syndrome should be considered in patients with unexplained multisystem disease, particularly edema or polyserous effusions accompanied by pulmonary hypertension and renal impairment. Negative routine M-protein testing should not exclude the diagnosis; VEGF testing, bone marrow evaluation, and extended IFE may reveal an occult plasma-cell clone.