AN ATYPICAL CAUSE OF EOSINOPHILIA AND HYPOCOMPLEMENTEMIA

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<h3>Introduction</h3> IgG4-related disease (IgG4-RD) is a multiorgan immune-mediated fibroinflammatory condition. Patients with IgG4-RD develop symptoms related to the tumor-like enlargement of affected tissues. Histopathologic studies demonstrate a lymphoplasmacytic infiltrate enriched in IgG4-positive plasma cells and a variable degree of storiform pattern fibrosis. <h3>Case Description</h3> A 76-year-old female patient with a history of hypergammaglobulinemia, lymphadenopathy, and Sjogren's syndrome was referred to our division due to low complement levels. She had no history of angioedema or urticaria. Laboratory studies showed hypocomplementemia with low levels of C3 (63 mg/dL), C4 (4 mg/dL), and CH50 (8 U/mL). Also hypergammaglobulinemia (3030 mg/dL) with elevated IgG4 (434 mg/dL), and an increased absolute eosinophil count (790 cells/µL). Skin biopsy on her left calf revealed granular deposition of IgG4. <h3>Discussion</h3> Here we present the case of IgG4-RD as an atypical cause of eosinophilia and hypocomplementemia. The presence of these findings in older patients with unexplained swelling in one or more organs that is responsive to corticoid therapy should raise the suspicion for IgG4-RD. It is important to note that approximately one third of patients diagnosed with IgG4-RD have hypocomplementemia. Interestingly, a case series of patients with IgG4-RD described an association of hypocomplementemia with increased severity and higher risk of relapse. Additionally, hypocomplementemia is related to renal involvement, specifically tubulointerstitial nephritis (TIN). In this regard, a case series reported that up to 56% of patients with IgG4-TIN have decreased C3 and C4.