A prospective observational study

Hereditary angioedema (HAE) with deficiency of C1 inhibitor (C1-INH) is an autosomal-dominant disease characterized by recurrent episodes of potentially life-threatening angioedema. The objective is to study the incidence of HAE among patients who visit the emergency department. This was a 3-year prospective observational screening study involving 13 urban tertiary emergency centers in Osaka prefecture, Japan. Patients were included if they met the following criteria: unexplained edema of the body, upper airway obstruction accompanied by edema, anaphylaxis, acute abdomen with intestinal edema (including ileus and acute pancreatitis), or asthma attack. C1-INH activity and C4 level were measured at the time of emergency department admission during the period between July 2011 and June 2014. This study comprised 66 patients with a median age of 54.0 (IQR: 37.5–68.3) years. Three patients were newly diagnosed as having HAE, and 1 patient had already been diagnosed as having HAE. C1-INH activity levels of the patients with HAEwere below the detection limit (<25%), whereas those of non-HAE patients (n = 62) were 106% (IQR: 85.5%–127.0%) (normal range, 70%–130%). Themedian level of C4 was significantly lower in the patients with HAE compared with those without HAE (1.2 [IQR: 1–3] mg/dL vs 22 [IQR: 16.5–29.5] mg/dL, P<0.01) (normal range, 17–45mg/dL). Three patients with undiagnosed HAE were diagnosed as having HAE in the emergency department during the 3-year period. If patients have signs and symptoms suspicious of HAE, the levels of C1-INH activity and C4 should be measured. Abbreviations: BUN = blood urea nitrogen, C1-INH = C1 inhibitor, CRE = creatinine, CRP = C-reactive protein, GOT = glutamic oxaloacetic transaminase, GPT = glutamic pyruvic transaminase, HAE = hereditary angioedema, IgE = immunoglobulin E, IQR = interquartile range, LDH = lactate dehydrogenase, TP = total protein, WBC = white blood cells.