Genetic Variation of Kallikrein-Kinin System and Related Genes in Patients With Hereditary Angioedema.

Hereditary angioedema (HAE) is an autosomal dominant disease caused by C1-INH deficiency due to mutations in SERPING1 (C1-INH-HAE) in most of the cases, or by specific mutations in factor XII gene, F12 (F12-HAE). Identification of polymorphisms in the genes encoding proteins from key pathways driving HAE can help to understand how genetic diversity contributes to its phenotypic variability. Here, 15 genes related to the Kallikrein-Kinin System (KKS) were analyzed by next generation sequencing in 59 patients with C1-INH-HAE or F12-HAE from Brazil, Denmark and Spain, and 19 healthy relatives in a total of 31 families. We identified 211 variants, from which 23 occurred only in Danish subjects and 79 were found only in Brazilian individuals, resulting in 109/211 variations in common between European and Brazilian population in the HAE families analyzed. BDKRB2 and CPM presented a large number of variants in untranslated regions, 46/49 and 19/24, respectively; whereas ACE (n = 26), SERPING1 (n = 26), CPM (n = 24), and NOS3 (n = 16) genes presented the higher number of variants directly affecting amino acid sequence. Despite the large amount of variants identified, the lack of association between genotype and phenotype indicates that the modulation of HAE symptom requires a more complex regulation, probably involving pathways beyond the KKS, epigenetics and environmental factors. Considering the new HAE types recently described, molecules involved in the regulation of vasculature and in plasminogen activation become promising targets for future genetic studies.

Health-related quality of life in Danish children with hereditary angioedema.

BACKGROUND: The potentially life-threatening disease hereditary angioedema with C1-inhibitor deficiency (C1-INH-HAE) can have considerable impact on the health-related quality of life (HRQoL) in adult patients. Half the patients with C1-INH-HAE develop symptoms before the age of 10 years. However, the HRQoL in children with C1-INH-HAE is almost unexplored. OBJECTIVE: To investigate HRQoL in Danish children with C1-INH-HAE, including possible correlations to disease severity and attack frequency. METHODS: All Danish children ages 2-18 years with C1-INH-HAE were invited to complete questionnaires regarding HRQoL; 14 (93%) agreed. Child self-report forms were used for children ages ≥5 years. The instruments used were the PedsQL (Child Self-Report and Parent Proxy-Report forms); the Children's Dermatology Life Quality Index; a nonvalidated, disease-specific quality-of-life questionnaire; and two visual analog scales that rated general health. RESULTS: The HRQoL scores in our study were comparable with the normal scores for healthy children and better than the scores in the only other study dedicated to HRQoL in children. Children with recent attacks had lower scores, whereas HRQoL scores were not correlated to overall disease severity or age. Surprisingly, home therapy was associated with lower HRQoL; however, home therapy was also correlated to a higher overall severity score and more frequent attacks. There was a strong child-parent agreement in the PedsQL forms, but scores were independent of whether the child had a family history of C1-INH-HAE or sporadic C1-INH-HAE and whether the parent completing the Parent Proxy-Report form carried the disease. CONCLUSION: Overall, the children assessed on average had a normal HRQoL and better than those with other common skin disorders. However, according to our findings, health care providers should be especially attentive to HRQoL when children with C1-INH-HAE become symptomatic.

Complement factor C4 activation in patients with hereditary angioedema.

OBJECTIVES: Low complement factor C4 is usually considered a valuable screening tool for patients with the potentially life-threatening hereditary angioedema with C1-inhibitor (C1-INH) deficiency (C1-INH-HAE). However, there are patients with C1-INH-HAE presenting with normal C4 levels. This means, that C1-INH-HAE may potentially be overlooked, if screening is performed only by measurement of C4. It has been suggested that measurement of C4 activation products is better suited to avoid false negative results. Our aim was to investigate whether total antigenic C4 or non-functional C4c is a better measure of the increased C4 activation in C1-INH-HAE patients. DESIGN AND METHODS: Two different monoclonal antibodies (mAb) to human C4 were produced: one had specificity for the ß-chain of C4 and would thus react with both functional and non-functional C4, and the other was developed against the factor I cleavage site on the α3-domain of C4 and was thus specific for activated, non-functional C4c. With these mAb we investigated plasma from 19 Danish C1-INH-HAE patients in three different enzyme-linked immunosorbent assays (ELISAs): a total antigenic C4 assay, a functional C4 assay and an assay measuring non-functional C4c. RESULTS: The amount of total antigenic C4 varied considerably between patients and 2 patients had total antigenic C4 levels in the normal area. Functional C4 was low in all C1-INH-HAE patients. A C4c/C4 ratio showed that around half the C4 measured in patients was non-functional and captured all C1-INH-HAE patients. CONCLUSIONS: This study shows that the C4c/C4 ratio seems to be a better diagnostic measure than total antigenic C4 alone. Our findings underline that screening with total antigenic C4 implies a risk of overlooking C1-INH-HAE patients.

Clinical characteristics and real-life diagnostic approaches in all Danish children with hereditary angioedema.

BACKGROUND: With a potentially early onset, hereditary angioedema (HAE) requires special knowledge also in infancy and early childhood. In children from families with HAE, the diagnosis should be confirmed or refuted early, which can be difficult. Studies of childhood HAE and the diagnostic approaches are limited. Our aim was to investigate the entire Danish cohort of children with HAE and non-HAE children of HAE patients for diagnostic approaches and clinical characteristics. RESULTS: We included 41 children: 22 with HAE and 19 non-HAE. Of the HAE children, 14 were symptomatic-median age at onset was 4 [1-11] years. The first attack was peripheral in 8/14 children and abdominal in 6/14 children, i.e. no one had their first attacks in the upper airways. Most children had less than one attack per month. All of the symptomatic children had been treated with tranexamic acid and/or C1 inhibitor concentrate. Unlike in other countries, androgens were not used in our pediatric cohort. Home therapy with C1 inhibitor concentrate was established in 9 cases: 6 children were trained in self-administration and 3 children were treated by parents. Of the children, 10 had been diagnosed by symptoms, including 3 without family history-median age of diagnosis among these children was 5.35 [2-13.2] years. In 31 children, HAE was diagnosed or refuted before symptoms by blood samples. In 23 of these children, complement values were investigated, and in 9 cases genetic testing was added to the complement measurements. In 8 children recently investigated, genetic testing was first choice. Cord blood was used for complement measurements in 9 children and for genetic testing in 4 children. Results of complement measurements were equivocal in several cases, especially in the cord blood samples, and the sensitivity of low complement C4 for the diagnosis of HAE was 75%. CONCLUSIONS: We investigated clinical characteristics in all Danish children with HAE. The rate of home therapy was high and androgens had been avoided. Complement values were often equivocal, especially in cord blood samples. Consequently, we have changed diagnostic practice to early genetic testing in children where the family mutation is known.

Psychometric Field Study of Hereditary Angioedema Quality of Life Questionnaire for Adults: HAE-QoL.

BACKGROUND: Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) may affect health-related quality of life (HRQoL). A specific HRQoL questionnaire for adult patients with C1-INH-HAE, the HAE-QoL, has recently been developed in Spain. OBJECTIVE: The objective of this study was to perform a cross-cultural validation and psychometric study of the HAE-QoL in an international setting. METHODS: Cross-cultural adaptation of the Spanish HAE-QoL draft version and an international rating phase with experts were performed. The resultant version of the HAE-QoL, a clinical questionnaire, and Short Form 36-item Health Survey Version 2.0 (SF-36v2) were pilot tested internationally. Item reduction was based on both descriptive and exploratory factor analysis. Psychometric properties were assessed. RESULTS: Cross-cultural adaptation of the HAE-QoL was performed in 18 countries. The draft version of the HAE-QoL was pilot tested in 332 patients, and accurate data were obtained from 290 patients from 11 countries. The reduction process resulted in a new version with 25 items and 7 dimensions (treatment difficulties, physical functioning and health, disease-related stigma, emotional role and social functioning, concern about offspring, perceived control over illness, and mental health). Strong psychometric properties were observed (Cronbach's α 0.92; test-retest reliability 0.87). Convergent validity showed mild to moderate correlations with SF-36v2 physical and mental component summaries (0.45 and 0.64, respectively) and with SF-36v2 dimensions (P < .004). HAE-QoL scores discriminated significantly among severity groups (median: asymptomatic 133.5 vs severe 84.0; P < .001); between patients with and without long-term prophylaxis (median: 101 vs 90; P = .001); and between patients with and without psychiatric and/or psychological care (median: 74 vs 103; P ≤ .001). CONCLUSIONS: The HAE-QoL, currently available in 18 languages, showed good reliability and validity evidence.

A specific assay for quantification of human C4c by use of an anti-C4c monoclonal antibody.

The increasing evidence of the implication of the complement system in the pathogenesis of several diseases has emphasized the need for the development of specific and valid assays, optimized for quantitative detection of complement activation in vivo. In the present study, we have developed a mouse monoclonal antibody (mAb) that is able to detect fluid phase C4c without interference from other products generated from the complement component C4. The C4c specific mAb was tested in different enzyme-linked immunosorbent assay (ELISA) combinations with various types of in vitro activated sera and samples from factor I deficient patients. The specificity of the mAb was further evaluated by immunoprecipitation techniques and by analysis of eluted fragments of C4 after immunoaffinity chromatography. The anti-C4c mAb was confirmed to be C4c specific, as it showed no cross-reactivity with native (un-cleaved) C4, C4b, iC4b, or C4d. Also, no reaction was observed with C4 fragments in factor I deficient plasma or serum samples. We established and validated a sandwich ELISA based on this C4c specific antibody. The normal range of C4c in EDTA/futhan plasma collected from 100 Danish blood donors was measured, with a mean of 0.85mg/L and a range of 0.19-2.21mg/L. We believe that the C4c specific antibody and the ELISA might be important tools in the future assessment of in vivo activation in situations where the classical or the lectin complement pathways are involved in the pathogenesis.

[Several new treatment possibilities of hereditary angio-oedema]. / Flere nye behandlingsmuligheder ved hereditært angioødem.

Hereditary angio-oedema (HAE) is a rare genetic disease caused by deficiency of complement C1 inhibitor. It is characterised by recurrent episodes of subcutaneous or submucosal oedema typically involving the extremities, bowel, face or larynx. Within the latest years it has become evident that the active mediator of HAE attacks is an increased level of bradykinin and various new treatment modalities have been developed. The aim of this paper is to give an update from the Danish HAE Comprehensive Care Centre on current treatment possibilities and address some of the challenges when diagnosing HAE.