Case Report: two cases of idiopathic plasmacytic lymphadenopathy subtype of idiopathic multicentric Castleman disease with xanthelasma palpebrum from a Canadian center

Idiopathic plasmacytic lymphadenopathy is a newly recognized subtype of idiopathic multicentric Castleman disease (iMCD-IPL) and often mimics IgG4-related disease (IgG4-RD). We present two of the first cases of iMCD-IPL diagnosed in British Columbia, Canada. Both patients had normolipemic bilateral xanthelasma palpebrum, which has not previously been reported in iMCD-IPL. Both patients were Asian women in the 5 th decade who presented with anemia, inflammation, polyclonal hypergammaglobulinemia (PHGG), and xanthelasmas. IgG4-RD was initially suspected, but upon review of the lymph node histology and careful clinicopathological correlation, both were found to have iMCD-IPL with plasmacytic histology. Biopsies of the xanthelasmas revealed foamy macrophages consistent with common xanthelasmas. Both patients had partial clinical and biochemical response to siltuximab, but no change in xanthelasmas. We searched the literature and identified three cases of unicentric Castleman’s disease (UCD) with xanthomas, systemic inflammation and PHGG. These three patients showed marked improvement in both systemic symptoms and xanthomas after resection of the UCD. We report two patients with normolipemic xanthelasmas and iMCD-IPL whose xanthelasmas did not regress with siltuximab. However, the regression of xanthomas in three cases of UCD from the literature suggest a potential pathophysiological association between Castleman disease and xanthomas.