Striking effectiveness of siltuximab-based treatment in refractory idiopathic multicentric Castleman disease resembling IgG4-related disease.
Xing Gong, Weiwei Yan, Feng Zhang et al.
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Case in brief
A 38-year-old man presented with persistent dry cough, generalized lymphadenopathy, and fatigue, with elevated serum IgG4. Inguinal lymph node biopsy showed plasma cell-type multicentric Castleman disease, including atrophic lymphoid follicles and marked plasma cell infiltration. Immunostaining found more than 50 IgG4-positive plasma cells per high-power field and an IgG4/IgG ratio of 40%, supporting idiopathic plasmacytic lymphadenopathy subtype of iMCD. Following a siltuximab-based regimen and radiotherapy, he achieved partial remission.
What made this case unusual
The iMCD-IPL presentation had elevated IgG4 and tissue findings resembling IgG4-related disease, creating diagnostic overlap between these systemic immune-mediated disorders.
Diagnostic / clinical pearl
Elevated serum IgG4 and abundant IgG4-positive cells in a lymph node can occur in iMCD-IPL; interpret these findings alongside the broader histopathology rather than assuming IgG4-related disease.