Hereditary angioedema is mostly heterozygous pathogenic variants in the C1NH gene. Familial cases are known-usually they have similar manifestations. If one sibling is affected and tested for mutations, and pathogenic variant has been identified; the same variant is likely to be causative in brother or another affected sibling. If the mutation was identified in sister by next generation sequencing (NGS); the brother can be tested for the same variant by Sanger sequencing. Sometimes homozygous or compound heterozygous variants also cause severe disease. In acquired forms of hereditary angioedema, the symptoms are usually much milder.