A large heterozygous deletion including the entire C1 inhibitor gene in a sporadic case of hereditary angio‐oedema

C1 inhibitor (C1‐INH) deficiency [hereditary or acquired angio‐oedema (HAE or AAE)] is characterized by recurring episodes of subcutaneous or submucosal oedema. Many different mutations in the C1‐INH gene have been identified as a cause of HAE. We investigated the molecular basis of the disease in a Japanese woman with sporadic HAE. Direct sequencing of genomic DNA revealed no point mutation in the C1‐INH gene. Quantitative real‐time PCR showed that the copy number of the C1‐INH gene in the patient was half that of a healthy control. Furthermore, we identified a 650‐kbp deletion on the chromosome, which included the C1‐INH gene. We evaluated the correlation between the patient’s attacks and her coagulation activity. The levels of D‐dimer were high during the angio‐oedema attacks, and often exceeded the normal range even during remission, thus the level of D‐dimer reflected the activity of HAE in this patient.