A Case of Angioedema Associated with Decreased C1 Inhibitor Activity

Background: We report a case of a 31-year-old woman who began to notice swelling of her arms at age 20. She was once given a diagnosis of cellulitis, but her symptoms spontaneously resolved. The patient had swelling of the left forearm and palm and was referred to our department for evaluation. She had slight pain but no obvious weight gain. Case Summary: Antinuclear antibody and other autoantibodies, including anti-ds-DNA antibody, anti-RNP antibody, anti-Sm antibody, and anti-SS-A antibody were not detected. C1 inhibitor activity was low, C3 was normal, C4 was low, CH50 was low, and C1q was normal. Discussion: Based on the presence of the typical clinical features and the positive results on the complement tests, we diagnosed hereditary angioedema. A decrease in C1 inhibitor activity and an increase in specific protein concentrations indicated type 1.