Angioedema as the first presentation of B-cell non-Hodgkin lymphoma – an unusual case with normal C1 esterase inhibitor level: a case report

BACKGROUND: Acquired angioedema is a rare but recognized manifestation of lymphoproliferative disorders due to deficiency in C1 esterase inhibitor. Normal level of C1 esterase inhibitor proteins in association with angioedema due to lymphoproliferative disease is a rare and an uncommon finding caused by antibodies produced from the underlying disease. Antibodies cause inactivation of C1 esterase inhibitor, thus resulting in C1 esterase inhibitor dysfunction despite of normal quantity of C1 esterase inhibitor. CASE PRESENTATION: A 50-year-old Sri Lankan male presented with first episode of angioedema without any family history. Physical examination revealed mild pallor with swelling of tongue, lips and perioral region. On investigations, erythrocyte sedimentation rate was persistently high and bone marrow with immunohistochemistry revealed infiltration with B-cell type low grade non-Hodgkin lymphoma. Computed tomography scan of the chest and abdomen showed paratracheal and subcarinal lymphadenopathy and splenomegaly, with the findings being compatible with lymphoma. He had normal C1 esterase inhibitor protein level with reduced activity and low C1q, C4 levels indicating antibodies against C1 esterase inhibitor causing dysfunctional C1 esterase inhibitor. CONCLUSION: Adult onset angioedema should prompt physicians to suspect underlying lymphoproliferative disorder despite of C1 esterase inhibitor protein level being normal. Though uncommon, presence of antibodies against C1 esterase inhibitor secondary to lymphoproliferative disorder should be considered in the presence of normal C1 esterase inhibitor protein levels with low functional capacity in the background of acquired angioedema.