Subcutaneous administration of C1 inhibitor concentrate: Case report of a pediatric patient with hereditary angioedema

ABSTRACT

Case report Background: Hereditary angioedema (HAE) is a rare disease that usually manifests during childhood and is characterized by recurrent swelling episodes in various body tissues. Effective treatment options, including replacement therapy with C1 inhibitor (C1-INH) concentrate, are available for acute attacks and, for patients with high disease burden, for prophylaxis. More convenient than intravenous (IV) injections, and better suitable for patients with difficult venous access, is subcutaneous (SC) administration. However, treatment with SC prophylactic C1-INH is not yet approved in Europe for children < 12 years of age. Case Description The boy presented to our clinic in 2014 at the age of 3, with a diagnosis of HAE due to C1-INH deficiency. During the last 3 months, he had been given IV C1-INH concentrate on-demand for HAE attacks. During the following year, the boy experienced monthly attacks at different body sites and had to be hospitalized several times for edema of the extremities and face, and abdominal colicky pain. At 5 to 6 years of age, attack frequency increased to once weekly and a first swelling of the trachea with dyspnea occurred. Over time, this led to repeated occurrence of panic attacks and psychological problems, which were exacerbated by social distancing during the coronavirus disease-19 pandemic. To mitigate disease burden, his therapy was switched to weekly prophylaxis with IV C1-INH, and the bradykinin receptor inhibitor icatibant was kept on hand as emergency medicine. Less than half a year later, attack frequency increased again and the regimen was changed to twice weekly. This led to drastic deterioration of venous access, so that a switch to SC prophylaxis became inevitable. The patient, now 10 years old, and his mother were trained in SC injection techniques and since June 2021, they administer twice weekly SC C1-INH (2000 International Units) at home, with no breakthrough attacks and significant improvement of quality of life. Conclusion(s) Because of high disease burden and impairment of quality of life due to high edema frequency, routine prophylaxis was chosen. In patients receiving frequent IV prophylaxis, occurrence of breakthrough attacks and deterioration of venous access warrants a switch to SC treatment. In the present case, this switch was unavoidable, although this treatment option is not approved for children. It allows the boy to self-administer his C1-INH and has improved his quality of life significantly.