[Hereditary angioedema causing colocolic intussusception]

International consensus on the diagnosis and management of pediatric patients with hereditary angioedema with C1 inhibitor deficiency

Background

The consensus documents published to date on hereditary angioedema with C1 inhibitor deficiency (C1‐INH‐HAE) have focused on adult patients. Many of the previous recommendations have not been adapted to pediatric patients. We intended to produce consensus recommendations for the diagnosis and management of pediatric patients with C1‐INH‐HAE.

Methods

During an expert panel meeting that took place during the 9th C1 Inhibitor Deficiency Workshop in Budapest, 2015 (www.haenet.hu), pediatric data were presented and discussed and a consensus was developed by voting.

Results

The symptoms of C1‐INH‐HAE often present in childhood. Differential diagnosis can be difficult as abdominal pain is common in pediatric C1‐INH‐HAE, but also commonly occurs in the general pediatric population. The early onset of symptoms may predict a more severe subsequent course of the disease. Before the age of 1 year, C1‐INH levels may be lower than in adults; therefore, it is advisable to confirm the diagnosis after the age of one year. All neonates/infants with an affected C1‐INH‐HAE family member should be screened for C1‐INH deficiency. Pediatric patients should always carry a C1‐INH‐HAE information card and medicine for emergency use. The regulatory approval status of the drugs for prophylaxis and for acute treatment is different in each country. Plasma‐derived C1‐INH, recombinant C1‐INH, and ecallantide are the only agents licensed for the acute treatment of pediatric patients. Clinical trials are underway with additional drugs. It is recommended to follow up patients in an HAE comprehensive care center.

Conclusions

The pediatric‐focused international consensus for the diagnosis and management of C1‐INH‐HAE patients was created.

Hereditary angioedema in childhood: an approach to management

Hereditary angioedema (HAE) is an inherited disorder characterized by recurrent, circumscribed, non-pitting, non-pruritic, and rather painful subepithelial swelling of sudden onset, which fades during the course of 48-72 hours, but can persist for up to 1 week. Lesions can be solitary or multiple, and primarily involve the extremities, larynx, face, esophagus, and bowel wall. Patients with HAE experience angioedema because of a defective control of the plasma kinin-forming cascade that is activated through contact with negatively charged endothelial macromolecules leading to binding and auto-activation of coagulation factor XII, activation of prekallikrein to kallikrein by factor XIIa, and cleavage of high-molecular-weight kininogen by kallikrein to release the highly potent vasodilator bradykinin. Three forms of HAE have currently been described. Type I and type II HAE are rare autosomal dominant diseases due to mutations in the C1-inhibitor gene (SERPING1). C1-inhibitor mutations that cause type I HAE occur throughout the gene and result in truncated or misfolded proteins with a deficiency in the levels of antigenic and functional C1-inhibitor. Mutations that cause type II HAE generally involve exon 8 at or adjacent to the active site, resulting in an antigenically intact but dysfunctional mutant protein. In contrast, type III HAE (also called estrogen-dependent HAE) is characterized by normal C1-inhibitor activity. The diagnosis of HAE is suggested by a positive family history, the absence of accompanying pruritus or urticaria, the presence of recurrent gastrointestinal attacks of colic, and episodes of laryngeal edema. Estrogens may exacerbate attacks, and in some patients attacks are precipitated by trauma, inflammation, or psychological stress. For type I and type II HAE, diminished C4 concentrations are highly suggestive for the diagnosis. Further laboratory diagnosis depends on demonstrating a deficiency of C1-inhibitor antigen (type I) in most kindreds, but some kindreds have an antigenically intact but dysfunctional protein (type II) and require a functional assay to establish the diagnosis. There are no particular laboratory findings in type III HAE. Prophylactic administration of either 17alpha-alkylated androgens or synthetic antifibrinolytic agents has proven useful in reducing the frequency or severity of attacks. Plasma-derived C1-inhibitor concentrate, recombinant C1-inhibitor, ecallantide (DX88; a plasma kallikrein inhibitor) and icatibant (a bradykinin B(2) receptor antagonist) have demonstrated significant efficacy in the treatment of acute attacks, whereas the C1-inhibitor concentrate has also provided a significant benefit as long-term prophylaxis. However, these drugs are not licensed in all countries and are not always readily available.

Pediatric hereditary angioedema due to C1-inhibitor deficiency

Hereditary angioedema (HAE) resulting from the deficiency of the C1 inhibitor (C1-INH) is a rare, life-threatening disorder. It is characterized by attacks of angioedema involving the skin and/or the mucosa of the upper airways, as well as the intestinal mucosa. In approximately 50 per cent of cases, clinical manifestations may appear during childhood. The complex management of HAE in pediatric patients is in many respects different from the management of adults. Establishing the diagnosis early, preferably before the onset of clinical symptoms, is essential in cases with a positive family history. Complement studies usually afford accurate diagnosis, whereas molecular genetics tests may prove helpful in uncertain cases. Appropriate therapy, supported by counselling, suitable modification of lifestyle, and avoidance of triggering factors (which primarily include mechanical trauma, mental stress and airway infections in children) may spare the patient unnecessary surgery and may prevent mortality. Prompt control of edematous attacks, short-term prophylaxis and intermittent therapy are recommended as the primary means for the management of pediatric cases. Medicinal products currently used for the treatment of children with hereditary angioedema include antifibrinolytics, attenuated androgens, and C1-INH replacement therapy. Current guidelines favour antifibrinolytics for long-term prophylaxis because of their favorable safety profile but efficacy may be lacking. Attenuated androgens administered in the lowest effective dose are another option. C1-INH replacement therapy is also an effective and safe agent for children. Regular monitoring and follow-up of patients are necessary.