Introduction
Castleman disease (CD) is a rare non-neoplastic disorder presenting as lymphadenopathy. Skin involvement and progression to lymphomas are uncommon, and such presentation can pose a diagnostic challenge. We describe an interesting case of multicentric CD presenting as a rash.
Case Description
A 79-year-old male presented with a 1-year history of blanchable maculopapular rash and new onset dyspnea in the absence of fever, fatigue or weight loss. Examination revealed axillary, cervical and inguinal lymphadenopathy, and firm splenomegaly. Initial labs were notable for leukocytosis, occasional lymphoplasmacytic cells, anemia, thrombocytopenia, negative HIV screen, and elevated ESR and LDH. Further testing identified polyclonal hypergammaglobulinemia. CT scans revealed generalized lymphadenopathy, splenomegaly with infarcts and unilateral pleural effusion. An inguinal lymph node needle biopsy, skin biopsy and pleural fluid cytology were concerning for lymphoplasmacytic, so he was started on rituximab and bendamustine. However, B cell clonality could not be demonstrated, making these findings concerning for Castleman disease.
Results
Human herpesvirus 8 (HHV-8) testing performed on the inguinal lymph node sample came out positive, and he was diagnosed with HHV-8 positive multicentric Castleman disease and continued on weekly rituximab. He demonstrated an excellent response with complete resolution of rash, palpable lymphadenopathy and anemia after 4 cycles of treatment.
Discussion
Castleman disease (CD) is a rare disorder of polyclonal B cell proliferation classically presenting as lymphadenopathy with constitutional symptoms. Cutaneous presentations include eruptive angiomas or petechial rash but can be variable. Intrinsic or viral IL-6 play a key role in the pathogenesis of the disease. CD can be localised or multicentric (related to HHV-8 +/- HIV or idiopathic), and these subtypes differ in prognosis and management, with HIV and HHV-8 co-positivity indicating worse outcomes. While human IL-6 in unicentric and idiopathic multicentric disease respond well to IL-6 receptor antagonists, viral IL-6 in HHV-8 associated cases has a limited response. This is the rationale for preferring anti-CD20 therapy with rituximab in these patients.
Conculsions
Correct biopsy specimen, keen analysis of distinct pathologic features, and HHV-8 testing on tissue sample guide the diagnosis as HHV-8 serology can be falsely negative.
