Etiologies

Infectious AAAs account for a third of aortic aneurysms reported in children. Such aneurysms are most commonly associated with umbilical artery catheterizations (UACs), with the need for repeated insertion or prolonged use of UAC resulting in increased risk. These AAAs are typically saccular, and rupture is the most serious sequela. They typically manifest in the newborn period, and more than 75% are associated with a Staphylococcus aureus or Staphylococcus albus infection, although polymicrobial infections are not rare. Their distribution is variable. More than half of these aneurysms affect the abdominal aorta, but the thoracic aorta and iliac vessels may also be involved (Figure 1).

Most infectious AAAs associated with UAC are recognized in the first 2 years of life. However, a history regarding the use of UACs is requisite for children of any age with an AAA, because presentation may be significantly delayed. Most of these aneurysms ultimately require an operation, but rare cases of spontaneous resolution have been reported in the literature. It is critical when undertaking surgery for these AAAs that there be no active infection, especially if the intervention might require placement of a prosthetic graft.

Takayasu’s aortoarteritis, a noninfectious inflammatory disease, is an exceedingly rare cause of pediatric AAAs. Aortic involvement with Takayasu’s disease is more often stenotic, and when aneurysms do exist they usually involve the thoracic aorta, not the abdominal aorta. Operative intervention in these cases of aortoarteritis carries risks of anastomotic disruption or narrowing if the intervention is undertaken in the face of active disease.

A considerable number of childhood AAAs occur in association with a genetic disease known to have vascular complications, including Ehlers–Danlos syndrome (EDS), Marfan’s syndrome, and tuberous sclerosis. Each deserves comment.

EDS results from abnormal collagen metabolism. The Villefranche classification includes six main types of this syndrome, with the vascular type representing type IV EDS. Type IV EDS is an autosomal dominant disease resulting from a defect in the COL3A1 gene for type III collagen. This disease is known for spontaneous ruptures of hollow viscera and large arteries including the aorta. In a review from the Mayo Clinic that encompasses a 30-year period, 132 vascular complications were identified in 24 patients with vascular-type EDS. Of those vascular complications, 17 had thoracic or abdominal aortic involvement and included arterial dissections or dissecting aneurysms or arterial ruptures. The youngest age at diagnosis in this series was 10 years.

One of the difficulties in determining the incidence of aortic aneurysm involvement with this syndrome is that the catastrophic complications occurring in childhood and resulting in death can happen without a defined diagnosis of vascular-type EDS. Surgical repair of aneurysms in these patients is hazardous because the vessels are fragile, and repair should be approached with caution.

Tuberous sclerosis is an autosomal dominant genetic disorder in which hamartomas in multiple organ systems are the dominant theme. Central nervous system involvement is common, and children often experience learning difficulties and seizure disorders. Renal, pulmonary, skin, or other organ systems may also be affected. Although uncommon, the association with aneurysms has been well described. The majority of aortic aneurysms are abdominal, and thoracic aortic involvement is less common (Figure 2). The age at AAA diagnosis is variable, but instances of rupture and death are known to have occurred in infancy and childhood.

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