Hypocomplementemic urticarial vasculitis syndrome is associated with high levels of serum IgG4: a clinical manifestation that mimics IgG4-related disease.

A 58-year-old Japanese woman presented with recurrent abdominal pain, chronic urticaria, and petechiae on her extremities, and hypocomplementemia, findings that were consistent with hypocomplementemic urticarial vasculitis syndrome (HUVS). A laboratory examination revealed that she had markedly elevated IgG levels (4,448 mg/dL; normal range, 870-1,700 mg/dL) with particularly high IgG4 levels (1,050 mg/dL; normal range, 48-105 mg/dL) and a high IgG4/total IgG ratio (0.22; normal range, 0.02-0.05). A skin biopsy demonstrated leukocytoclastic vasculitis with IgG4 deposition in the vascular lumen and vascular walls. A lymph node biopsy revealed reactive lymphoid hyperplasia with numerous IgG4-positive cells in the perifollicular area, but no sclerotic findings. A chromosomal analysis of an enlarged lymph node, without phytohemagglutinin (PHA) stimulation, demonstrated that one in every three analyzed cells had abnormalities, such as 44, XX, -13, add(15)(p11), -17, -17, and mar.