The Value of a Pet Scan in Selecting the Best Lymph Node to Biopsy, and Confirming the Diagnosis of Idiopathic Multicentric Castleman Disease with HLH And EBV Viremia in a Previously Healthy Adult.

INTRODUCTION

Castleman disease (CD) is a rare lymphoproliferative disorder having a variegated clinical presentation. Diagnosis of the idiopathic HIV- and HHV8-negative multicentric CD (iMCD) subtype poses a challenge given its non-specific clinical manifestations. iMCD presents as diffuse lymphadenopathy with inflammatory manifestations, primarily driven by interleukin-6 (IL-6). Treatment includes suppressing the inflammation by targeting IL-6 with monoclonal antibodies such as siltuximab and, in severe cases, immuno-chemotherapy to control B- and plasma-cell activation.

CASE DESCRIPTION

A previously healthy 43-year-old male presented to the emergency department with fever, night sweats, anasarca, anaemia, thrombocytopenia and acute renal insufficiency. Extensive blood and imaging workup was initiated. Several diagnoses were entertained including viral infections (comprising COVID-19), haemophagocytic lymphohistiocytosis, lymphoma and autoimmune conditions. Initial axillary lymph node biopsy was not diagnostics. A positron emission tomography (PET) scan showed diffuse and symmetrical cervical and hilar/mediastinal lymphadenopathies. A mediastinal lymph node biopsy was then performed and indicated iMCD. The patient was treated with high-dose steroids and siltuximab. An Epstein-Barr virus (EBV) PCR was positive, and rituximab was added to the treatment. The patient recovered and felt well after two months.

CONCLUSIONS

Non-specific symptoms, non-diagnostic first biopsy and iMCD resemblance to haemophagocytic lymphohistiocytosis further complicated the diagnosis. A PET scan allowed the best selection of a lymph node to be biopsied. Anti-IL6 is the recommended treatment; however, we are lacking information on the duration of siltuximab, and the long-term toxicity and immunosuppressive effect of this treatment. The contribution of EBV reactivation in the development and treatment of iMCD needs further investigation.

LEARNING POINTS

A positron emission tomography (PET) scan is important to identify the optimal lymph node biopsy site for diagnostics.Epstein-Barr virus reactivation has a role in the pathogenesis and treatment choice of idiopathic multicentric Castleman disease.