Imaging findings in a distinct lethal inherited arteriopathy syndrome associated with a novel mutation in the FBLN4 gene

Giant ascending aortic aneurysm with impending rupture as presentation of cutis laxa 1B: a case report

Background

Thoracic aortic aneurysms are rarely symptomatic but can result in acute aortic syndromes, associated with a high mortality rate. While most cases may be acquired, a genetic basis is evident in approximately 20-25% of the cases, especially among patients under 50 years of age, and those exhibiting syndromic features or family history. Although autosomal dominant inheritance is predominant in familial aortopathies, exceptions exist, such as cutis laxa 1B (CL1B)-related aortic disease, caused by variants in EFEMP2 gene, that follows an autosomal recessive inheritance pattern.

Case summary

We present the case of a 26-year-old male with a giant ascending aorta aneurysm and massive pericardial effusion, which was ultimately diagnosed of CL1B due to the p.Ser137Cys variant in the EFEMP2 gene in homozygosis. The patient underwent successful ascending aorta replacement (Bentall´s procedure). There were not complications or further events after 2 years of follow-up.

Discussion

This case underscores the importance of genetic testing in young patients presenting with aortopathies, syndromic features, or atypical presentations, irrespective of family history.

Severe Phenotype of Cutis Laxa Type 1B with Antenatal Signs due to a Novel Homozygous Nonsense Mutation in EFEMP2

EFEMP2 mutations are known to be responsible for autosomal recessive cutis laxa type 1B (ARCL1B), a rare multisystem disease affecting skin, skeleton, and vascular structures. We report 2 additional related cases of ARCL1B of particular severity leading to termination of pregnancy. Cardinal signs of this connective tissue disease were already seen during the second trimester of pregnancy, then confirmed and clarified at autopsy. Anomalies included cutis laxa, arachnodactyly, clubfoot, wormian bones, moderate bowing of long bones with slender bone trabeculae, rib fractures, undermuscularized diaphragm, hiatal hernia, and arterial tortuosity with thick vascular walls and disorganized elastic fibers. Sequencing of the EFEMP2 gene revealed a novel homozygous nonsense mutation: c.639C>A (p.Cys213*). We performed a thorough histological analysis and discuss differential diagnoses, genotype-phenotype correlations, and the challenge of prenatal diagnosis of this disease.

Valve-Sparing Root and Total Arch Replacement for Cutis Laxa Aortopathy

Aortic aneurysms requiring surgery in early childhood are rare. Herein we describe the case of a three-year-old with massive aneurysmal aortic dilation secondary to the rare and often lethal genetic disorder, cutis laxa. Initial thoracic aortic aneurysm gene panel was negative. Parents of the child were not known to be consanguineous, but high-density SNP array revealed several regions of homozygosity. This prompted targeted sequence analysis that identified a novel homozygous missense mutation in the gene for cutis laxa, EFEMP2. The patient underwent aortic valve-sparing aortic root and ascending aorta replacement and total aortic arch replacement, with continuous, moderately hypothermic cardiopulmonary bypass, using a dual cannulation technique. He was discharged well on the third postoperative day and remains free of aneurysmal disease at two-year follow-up.

Fibulin-4 is essential for maintaining arterial wall integrity in conduit but not muscular arteries

Homozygous or compound heterozygous mutations in fibulin-4 (FBLN4) lead to autosomal recessive cutis laxa type 1B (ARCL1B), a multisystem disorder characterized by significant cardiovascular abnormalities, including abnormal elastin assembly, arterial tortuosity, and aortic aneurysms. We sought to determine the consequences of a human disease-causing mutation in FBLN4 (E57K) on the cardiovascular system and vascular elastic fibers in a mouse model of ARCL1B. Fbln4E57K/E57K mice were hypertensive and developed arterial elongation, tortuosity, and ascending aortic aneurysms. Smooth muscle cell organization within the arterial wall of large conducting vessels was abnormal, and elastic fibers were fragmented and had a moth-eaten appearance. In contrast, vessel wall structure and elastic fiber integrity were normal in resistance/muscular arteries (renal, mesenteric, and saphenous). Elastin cross-linking and total elastin content were unchanged in large or small arteries, whereas elastic fiber architecture was abnormal in large vessels. While the E57K mutation did not affect Fbln4 mRNA levels, FBLN4 protein was lower in the ascending aorta of mutant animals compared to wild-type arteries but equivalent in mesenteric arteries. We found a differential role of FBLN4 in elastic fiber assembly, where it functions mainly in large conduit arteries. These results suggest that elastin assembly has different requirements depending on vessel type. Normal levels of elastin cross-links in mutant tissue call into question FBLN4's suggested role in mediating lysyl oxidase-elastin interactions. Future studies investigating tissue-specific elastic fiber assembly may lead to novel therapeutic interventions for ARCL1B and other disorders of elastic fiber assembly.

Familial thoracic aortic aneurysms

PURPOSE OF REVIEW

A lot of new data have been obtained in familial thoracic aortic aneurysms, including description of new entities and better understanding of pathophysiology. The aim of this review is to put them in perspective.

RECENT FINDINGS

The new data have been collected, put together, and allowed a new classification scheme to be proposed by the Montalcino Aortic Consortium on the basis of the role of proteins coded by the culprit gene (either protein of the extracellular matrix or protein of the transforming growth factor-beta pathway, or protein of the contractile apparatus of the smooth muscle cell). These groups of diseases include aortic aneurysm, but the extent of extra-aortic vascular risk and the presence of extra-aortic (skeletal, ophthalmologic, neurological, or immunological) features vary according to the gene involved. This understanding also sheds light on the therapeutic benefits that can be foreseen for new molecules, or old molecules used in a newer way.

SUMMARY

Classification of familial forms of thoracic aortic aneurysm should allow a better understanding of these diseases and therefore standardization of initial evaluation of the patients (vascular evaluation limited or not to the aorta, and extravascular evaluation, including or not skeleton, eyes, neurology, digestive tract, and immunological diseases) and individualization of therapy (adapted to both the genotype and the phenotype).