Familial Abdominal Aortic Aneurysms

Familial Incidence of Abdominal Aortic Aneurysms

The rupture of an abdominal aortic aneurysms (AAAs) is associated with a mortality rate exceeding 50%. To reduce this figure it is necessary to increase the frequency of early diagnosis and elective surgery. Screening the general population for occult AAAs has proven cost ineffective. Only by identifying high-risk subgroups will screening programs be improved. The aim of this report was to investigate by ultrasonography the prevalence of previously unknown aortic dilatations among first-degree relatives (parents, siblings, and children) of patients operated on for AAAs.

Ninety-one (52.6%) of the 173 living first degree-relatives of 51 patients who underwent AAA resection were submitted to an aortoiliac ultrasonographic examina tion to establish aortic diameter and morphology. There was at least 1 first-degree relative with an AAA (multiplex family) in 10 families (19.6%) before ultrasound screening. With ultrasound a previously unknown infrarenal aortic dilatation was detected in 14 subjects (9 men/5 women; 10 siblings and 4 children) of 12 different families. Specifically, these aortic dilatations consisted of 10 AAAs (diameters ranged from 2.6 to 4.3 cm) and 4 aortic blebs. These occult aortic dilatations were located in 50% of cases in the lower third of the infrarenal abdominal aorta. The cumulative incidence of multiplex families was 35.3%. This study suggests a familial tendency to have an important etiologic role in the formation of AAAs. Family screening of, above all, male siblings older than forty-five years will help identify occult AAAs and reduce the mortality rates associated with their rupture.

The Low Prevalence of Abdominal Aortic Aneurysm in Relatives in Northern Ireland

INTRODUCTION

Mortality from ruptured abdominal aortic aneurysm (AAA) remains high and has given impetus to screening. Targeted screening towards high-risk groups would increase efficacy. Relatives of previous AAA patients have been suggested as one such group. The aim of this study was therefore to determine the prevalence of AAA in relatives of previous patients in Northern Ireland.

PATIENTS AND METHODS

All living AAA patients, who underwent surgery between August 2001 and December 2005 in our unit, or were attending for follow-up of small aneurysms were contacted and asked for details of siblings and their family history. Screening by ultrasound was offered to the siblings and children over 50 years, with a defining threshold diameter for an aneurysm of 3.0 cm. Overall prevalence of AAA in the relatives was calculated. Separate prevalence rates were calculated according to relationship and gender of the patient and relative.

RESULTS

513 previous patients were contacted. 132 gave details of living relatives, resulting in a total of 405 relatives suitable for screening. 105 declined a scan, leaving 300 in the study. Overall mean age of the group was 63.0+/-8.7 years and 68% were siblings of male patients. Overall ten AAAs were detected by screening, giving a prevalence of 3.3%. No aneurysms were found in the subgroup of children, while the highest prevalence (12.5%) was found in brothers of female patients. 20 additional AAAs were reported in these 132 families, resulting in 14 of the 132 families (10.6%) having two or more members with AAA.

CONCLUSION

The prevalence of screening detected AAA in this study is lower than anticipated. The reason is unclear, but demonstrates the multifactorial nature of the aetiology and genetic complexities yet to be unravelled by future research.

Familial abdominal aortic aneurysm: a systematic review of a genetic background

BACKGROUND

Familial clustering of the abdominal aortic aneurysm (AAA) is clear, 12-19% of AAA patients have one or more first-degree relatives with an aneurysm and 4-19% is detected with ultrasound screening.

OBJECTIVES

To review the genetic background of AAA. DESIGN, METHODS AND MATERIALS: Computer searches of the MEDLINE, EMBASE, SUMsearch database and the Cochrane Library and searched reference lists of English language articles concerning the genetics of AAA, candidate gene approach and linkage analysis.

RESULTS

Brothers of AAA patients are at high risk to develop an AAA. The candidate gene approach was performed to detect defects in one of the components of the connective tissue, i.e. type I and III collagen, elastin and fibrillin, the inflammatory cell-derived matrix metalloproteinase, there inhibitors, auto-immune components and components related to atherosclerosis.

CONCLUSION

These studies give us insight in the pathology but do not lead to the specific genetic factor(s) responsible for (familial) AAA. Considering the supposed autosomal dominant inheritance, a gene mutation in one of the structural proteins of the connective tissue is expected. In the future, linkage analysis may resolve the genetic background of AAA.

The role of type III collagen in family members of patients with abdominal aortic aneurysms

OBJECTIVES

type III collagen is responsible for the tensile strength of the aorta-wall. To determine if genetic defect in the type III collagen production is associated with familial clustering of AAA.

METHODS

fifty-six patients with AAA and 82 first-degree family members participated. The medical and family histories were obtained. All these relatives were screened by ultrasound for AAA. In 58 relatives of 20 families, skin biopsies were taken for protein analysis to measure type III collagen production in cultured fibroblasts.

RESULTS

only one new AAA was detected in a brother of a patient. Four other relatives were already known with AAA. Three AAA patients had a type III collagen deficiency, but type III collagen was normal in all family members.

CONCLUSION

type III collagen deficiency does not appear to be an aetiological factor in the development of AAA.

Abdominal aortic aneurysm, glaucoma and deafness: a new familial syndrome

Several reports have suggested a genetic basis for the distribution of abdominal aortic aneurysm (AAA) in some families. The familial clustering of this disease is further demonstrated in this report of ten siblings, five of whom have confirmed AAA. This is the largest cluster so far reported. The majority of patients in this family group also have glaucoma and/or deafness.

Pathogenesis of acquired aneurysms of the abdominal aorta

The incidence of abdominal aortic aneurysm has recently increased. There is still no accurate definition of abdominal aortic aneurysm. The diameter of abdominal aortic aneurysms is the only factor permitting evaluation of the risk of rupture of aneurysms whose growth remains unpredictable. Abdominal aortic aneurysm is a multi-factorial disease associated with aortic aging and atheroma. It differs from stenotic disease by the intensity of degenerative or destructive phenomena in the media. Particular hemodynamic conditions in the infrarenal abdominal aorta seem to enhance the development of aneurysm at this level. While certain constitutional anomalies of the extracellular matrix of proteins seem to enhance the development of abdominal aortic aneurysm, protease activity of as yet undetermined origin also seems to play a prominent role. Family cases of abdominal aortic aneurysms have been reported but the mechanisms responsible remain to be determined. Several genetic markers have been suggested. The most reliable marker of aortic aneurysm is arteriomegaly.

On the inheritance of abdominal aortic aneurysm

To determine the mode of inheritance of abdominal aortic aneurysm, data on first-degree relatives of 91 probands were collected. Results of segregation analysis performed on these data are reported. Many models, including nongenetic and genetic models, were compared using likelihood methods. The nongenetic model was rejected; statistically significant evidence in favor of a genetic model was found. Among the many genetic models compared, the most parsimonious genetic model was that susceptibility to abdominal aortic aneurysm is determined by a recessive gene at an autosomal diallelic major locus. A multifactorial component in addition to the major locus does not increase the likelihood of the data significantly.