Atypical Combination of Mixed Connective Tissue Disease and Multicentric Castleman Disease

Area of Science:

• Hematology
• Immunology
• Oncology

Background:

• Castleman disease (CD) is a rare lymphoproliferative disorder with unicentric (UCD) and multicentric (MCD) forms.
• CD is often associated with human herpes virus-8 (HHV-8) and human immunodeficiency virus (HIV), particularly in its multicentric form.
• Mixed connective tissue disease (MCTD) is an autoimmune disorder with overlapping features of other connective tissue diseases.

Observation:

• A 68-year-old woman with diabetes and recent MCTD diagnosis presented with lymphadenopathy, splenomegaly, and B symptoms.
• Histopathological analysis revealed the plasma cell subtype of MCD with polyclonal plasmacytosis, negative for HIV and HHV-8.
• The patient experienced symptom resolution with rituximab and corticosteroids, followed by relapse and partial improvement with an anti-IL-6 agent.

Findings:

• This case presents a rare instance of the plasma cell subtype of MCD in an elderly patient with concurrent MCTD.
• The patient's presentation underscores the importance of considering CD in the differential diagnosis of lymphadenopathy with systemic symptoms.
• Chronic inflammation and B lymphocyte proliferation may indicate a potential link between MCTD and CD.

Implications:

• This case highlights the need for a high index of suspicion for CD, especially in patients with comorbidities and atypical presentations.
• Further research is warranted to explore the potential association between MCTD and CD.
• Individualized treatment strategies and close monitoring are crucial for managing CD due to its heterogeneity and risk of relapse.