Autosomal Recessive Cutis Laxa Research Articles

On the curious association of diaphragmatic hernia and Urban-Rifkin-Davis Syndrome (Autosomal Recessive Cutis Laxa-1C): A collective review of 16 cases

Background: Autosomal recessive cutis laxa type-1C is also known as Urban-Rifkin-Davis syndrome (URDS). It is known to affect cardiopulmonary, integumentary, gastrointestinal, musculoskeletal and genitourinary systems. However, its frequent association with congenital diaphragmatic hernia has not previously been highlighted. Case Presentation: A newborn male with cutis laxa presented with respiratory distress at birth. The cause of dyspnoea was perinatal strangulation of the stomach in hiatus hernia. After surgical repair of the hernia, his respiratory distress temporarily improved but kept recurring periodically by various mechanisms in sequence namely pulmonary hypertension, tracheomalacia, pulmonary emphysema and finally he succumbed to pneumothorax. Genetic analysis revealed his skin condition as autosomal recessive cutis laxa type-1C which is also known as URDS. Exome sequencing revealed a novel frameshift mutation c.426delC (p.Cys143Alafs*41) of the LTBP4 gene in the exon 5 of Chromosome 19. Conclusion: Out of the 28 cases of URDS reported in the world literature 57% had congenital diaphragmatic hernia (CDH) and 53% of them died during infancy. Such a high incidence of CDH is not observed in other subtypes of elastic disorders. Thus, congenital diaphragmatic defects appear to be a characteristic diagnostic feature of URDS in patients with cutis laxa.

Corkscrew Mesenteric Arteries and Tortuous Descending Aorta in Autosomal Recessive Cutis Laxa.

Corkscrew Mesenteric Arteries and Tortuous Descending Aorta in Autosomal Recessive Cutis Laxa.

Two novel homozygous variants of ATP6V0A2 and ALDH18A1 lead to autosomal recessive cutis laxa type 2 and 3 in two Pakistani families.

Autosomal recessive cutis laxa type 2A (ARCL2A; OMIM: 219200) is characterized by neurovegetative, developmental and progeroid elastic skin anomalies. It is caused by biallelic variation in ATPase, H+ transporting V0 subunit A2 (ATP6V0A2; OMIM: 611716) located on chromosome 12q24.31. Autosomal recessive cutis laxa type 3A (ARCL3A; OMIM: 219150) is another subclinical type characterized by short stature, ophthalmological abnormalities and a progeria-like appearance. The ARCL3A is caused by loss of function alterations in the aldehyde dehydrogenase 18 family member A1 (ALDH18A1; OMIM: 138250) gene located at chromosome 10q24.1. Whole-exome sequencing (WES), and Sanger sequencing were performed for molecular diagnosis. 3D protein modeling was performed to investigate the deleterious effect of the variant on protein structure. In this study, clinical and molecular diagnosis were performed for two families, ED-01 and DWF-41, which displayed hallmark features of ARCL2A and ARCL3A, respectively. Three affected individuals in the ED-01 family (IV-4, IV-5 and V-3) displayed sagging loose skin, down-slanting palpebral fissures, excessive wrinkles on the abdomen, hands and feet, and prominent veins on the trunk. Meanwhile the affected individuals in the DWF-41 family (V-2 and V-3) had progeroid skin, short stature, dysmorphology, low muscle tone, epilepsy, lordosis, scoliosis, delayed puberty and internal genitalia. WES in the index patient (ED-01: IV-4) identified a novel homozygous deletion (NM_012463.3: c.1977_1980del; p.[Val660LeufsTer23]) in exon 16 of the ATP6V0A2 while in DWF-41 a novel homozygous missense variant (NM_001323413.1:c.1867G>A; p.[Asp623Asn]) in exon 15 of the ALDH18A1 was identified. Sanger validation in all available family members confirmed the autosomal recessive modes of inheritances in each family. Three dimensional in-silico protein modeling suggested deleterious impact of the identified variants. Furthermore, these variants were assigned class 1 or "pathogenic" as per guidelines of American College of Medical Genetics 2015. Screening of ethnically matched healthy controls (n= 200 chromosomes), excluded the presence of these variations in general population. To the best of our knowledge, this is the first report of ATP6V0A2 and ALDH18A1 variations in the Pakhtun ethnicity of Pakistani population. The study confirms that WES can be used as a first-line diagnostic test in patients with cutis laxa, and provides basis for population screening and premarital testing to reduce the diseases burden in future generations.

A novel deletion mutation in the ATP6V0A2 gene in an Iranian patient affected by autosomal recessive cutis laxa.

Cutis laxa (CL) can be caused by mutations in a number of genes. Cutis laxa with autosomal recessive inheritance due to mutations in several genes, including mutations in the ATP6V0A2 gene, causes autosomal recessive cutis laxa type 2A (ARCL2A). The ATP6V0A2 gene encodes the a2 subunit in the V-ATPases pump. The V-ATPases are located in the membrane of some organelles, including the Golgi or some vesicles, and act as ATP-dependent proton pumps to pH adjustment intracellular segments. Mutations in the ATP6V0A2 gene consist present in ARCL2A patients. We present the case of a 12-year-old girl who was referred to Rasad Laboratory (Tehran, Iran) at the age of 5 with a set of symptoms of congenital disorders. Her clinical phenotype contains distal symmetrical sensory and motor polyneuropathy, loose joints, large nasal roots, growth delay, and wrinkled skin. Also, there was a history of the parental marriage of consanguinity. A potentially pathogenic homozygous deletion mutation was detected in the ATP6V0A2 gene related to ARCL2A. This mutation has not been reported in the other patients with ARCL2A. A novel homozygous deletion mutation in ATP6V0A2 is supposed to be the reason for disease in our proband.

Autosomal recessive cutis laxa type IIIA: Report of a patient with severe phenotype and review of the literature

Autosomal recessive cutis laxa type IIIA is a very rare genetic condition, caused by pathogenic variants in ALDH18A1, encoding delta-1-pyrroline-5-carboxylate synthase (P5CS). This enzyme catalyzes the reduction of glutamic acid to delta1-pyrroline-5-carboxylate, playing a key role in the de novo biosynthesis of proline, ornithine, and arginine. Autosomal recessive cutis laxa type IIIA is characterized by abundant and wrinkled skin, skeletal anomalies, cataract or corneal clouding and neuro-developmental disorders of variable degree.We report on a patient with autosomal recessive cutis laxa type IIIA, due to a homozygous missense c.1273C > T; p. (Arg425Cys) pathogenic variant in ALDH18A1. The patient presented a severe phenotype with serious urological involvement, peculiar cerebro-vascular abnormalities and neurodevelopmental compromise. This description contributes to better characterize the phenotypic spectrum associated with ALDH18A1 pathogenic variants, confirming the systemic involvement as a typical feature of autosomal recessive cutis laxa type IIIA.

Autosomal recessive cutis laxa type 1C with a homozygous LTBP4 splicing variant: a case report and update of literature

Autosomal recessive cutis laxa (ARCL) is a heterogeneous disorder with three primary forms (ARCL 1, ARCL 2 and ARCL 3). Latent transforming growth factor beta binding protein 4 (LTBP4) anomalies cause ARCL1C and are connected to different problems in the skin and other organs. Herein, we present a seven month old Iranian boy with a clinical manifestation of ARCL1 with literature review of previous cases with attributes of ARCL1C. Considering the craniofacial characteristics and respiratory distress of the proband, cutis laxa (CL) was expected and whole-exome sequencing (WES) was performed. In the proband, signs of CL were mainly located in the face, thorax, and abdomen. The prenatal investigation revealed a diaphragmatic hernia and certain uncommon signs, such as an atrial septal defect and pyloric stenosis. The WES showed a novel homozygous mutation (c.533-1G > A) in exon six of the LTBP4 gene. This report showed a new variant with uncommon clinical features, such as a stenosis atrial septal defect and pyloric stenosis, which causes ARCL1C. Unfortunately, the proband developed several heart problems and died at the age of seven months and seven days. Thus, a more in-depth evaluation is needed to clarify the different aspects of CL related to LTBP4 disorder.

Expanding the phenotypic spectrum of ALDH18A1-related autosomal recessive cutis laxa with a description of novel neuroradiological findings.

Pickwick, Charlottea; Callewaert, Bertb; van Dijk, Fleurc; Harris, Juliettec; Wakeling, Emmad; Hay, Eleanord; Yeo, Mildride; Chakrapani, Anupame; Baptista, Juliaf,g; Moore, Sandraf; Yoong, Michaelh; Chatterjee, Fionai; Ghali, Neetic Author Information

Autosomal Recessive Cutis Laxa 1C Mutations Disrupt the Structure and Interactions of Latent TGFβ Binding Protein-4.

Latent TGFβ binding protein-4 (LTBP4) is a multi-domain glycoprotein, essential for regulating the extracellular bioavailability of TGFβ and assembly of elastic fibre proteins, fibrillin-1 and tropoelastin. LTBP4 mutations are linked to autosomal recessive cutis laxa type 1C (ARCL1C), a rare congenital disease characterised by high mortality and severely disrupted connective tissues. Despite the importance of LTBP4, the structure and molecular consequences of disease mutations are unknown. Therefore, we analysed the structural and functional consequences of three ARCL1C causing point mutations which effect highly conserved cysteine residues. Our structural and biophysical data show that the LTBP4 N- and C-terminal regions are monomeric in solution and adopt extended conformations with the mutations resulting in subtle changes to their conformation. Similar to LTBP1, the N-terminal region is relatively inflexible, whereas the C-terminal region is flexible. Interaction studies show that one C-terminal mutation slightly decreases binding to fibrillin-1. We also found that the LTBP4 C-terminal region directly interacts with tropoelastin which is perturbed by both C-terminal ARCL1C mutations, whereas an N-terminal mutation increased binding to fibulin-4 but did not affect the interaction with heparan sulphate. Our results suggest that LTBP4 mutations contribute to ARCL1C by disrupting the structure and interactions of LTBP4 which are essential for elastogenesis in a range of mammalian connective tissues.

Congenital autosomal recessive cutis laxa 2A

Congenital cutis laxa is a rare inherited skin disorder and shows diverse phenotypic features among its different variants. Most forms are progressive and dysmorphic features worsen with age giving an appearance of early ageing. Autosomal recessive cutis laxa, type 2a, (ARCLIIa) is the only variant where phenotypic features undergo spontaneous regression and self-resolution with age. We are reporting a case of congenital ARCLIIa, in a child who had primarily presented with right-sided pneumonia. The child was investigated and worked up for cutis laxa based on skin appearance and characteristic facies (loose sagging skin, redundant skin folds, and hound-like facies). In view of history of a cousin having similar findings which had self-resolved overtime without any treatment, we further suspected it to be type 2A variant, which was proven by genetic analysis (ATP6V02 gene). Hence, we wish to report this case.

LTBP4 in Health and Disease.

Latent transforming growth factor β (TGFβ)-binding protein (LTBP) 4, a member of the LTBP family, shows structural homology with fibrillins. Both these protein types are characterized by calcium-binding epidermal growth factor-like repeats interspersed with 8-cysteine domains. Based on its domain composition and distribution, LTBP4 is thought to adopt an extended structure, facilitating the linear deposition of tropoelastin onto microfibrils. In humans, mutations in LTBP4 result in autosomal recessive cutis laxa type 1C, characterized by redundant skin, pulmonary emphysema, and valvular heart disease. LTBP4 is an essential regulator of TGFβ signaling and is related to development, immunity, injury repair, and diseases, playing a central role in regulating inflammation, fibrosis, and cancer progression. In this review, we focus on medical disorders or diseases that may be manipulated by LTBP4 in order to enhance the understanding of this protein.

SPG9A with the new occurrence of an ALDH18A1 mutation in a CMT1A family with PMP22 duplication: case report

BackgroundALDH18A1 mutations lead to delta-1-pyrroline-5-carboxylate-synthetase (P5CS) deficiency, which is a urea cycle-related disorder including SPG9A, SPG9B, autosomal dominant cutis laxa-3 (ADCL3), and autosomal recessive cutis laxa type 3A (ARCL3A). These diseases exhibit a broad clinical spectrum, which makes the diagnosis of P5CS deficiency difficult. We report here a rare Japanese family including both patients with an ALDH18A1 mutation (SPG9A) and ones with CMT1A.Case presentationA Japanese family included five patients with the CMT phenotype and five with the HSP phenotype in four generations. The patients with the HSP phenotype showed a pure or complicated form, and intrafamilial clinical variability was noted. Genetically, FISH analysis revealed that two CMT patients had a PMP22 duplication (CMT1A). Exome analysis and Sanger sequencing revealed five HSP patients had an ALDH18A1 heterozygous mutation of c.755G > A, which led to SPG9A. Haplotype analysis revealed that the ALDH18A1 mutation must have newly occurred. To date, although de novo mutations of ALDH18A1 have been described in ADCL3A, they were not mentioned in SPG9A in earlier reports. Thus, this is the first SPG9A family with a de novo mutation or the new occurrence of gonadal mosaicism of ALDH18A1. Analysis of serum amino acid levels revealed that two SPG9A patients and two unaffected family members had low citrulline levels and one had a low level of ornithine.ConclusionsSince the newly occurring ALDH18A1 mutation, c.755G > A, is the same as that in two ADHSP families and one sporadic patient with SPG9A reported previously, this genomic site might easily undergo mutation. The patients with the c.755G > A mutation in our family showed clinical variability of symptoms like in the earlier reported two families and one sporadic patient with this mutation. Further studies are required to clarify the relationship between the amino acid levels and clinical manifestations, which will reveal how P5CS deficiency influences disease phenotypes including ARCL3A, ADCL3, SPG9B, and SPG9A.

Expanding the clinical and molecular spectrum of ATP6V1A related metabolic cutis laxa.

Several inborn errors of metabolism show cutis laxa as a highly recognizable feature. One group of these metabolic cutis laxa conditions is autosomal recessive cutis laxa type 2 caused by defects in v‐ATPase components or the mitochondrial proline cycle. Besides cutis laxa, muscular hypotonia and cardiac abnormalities are hallmarks of autosomal recessive cutis laxa type 2D (ARCL2D) due to pathogenic variants in ATP6V1A encoding subunit A of the v‐ATPase. Here, we report on three affected individuals from two families with ARCL2D in whom we performed whole exome and Sanger sequencing. We performed functional studies in fibroblasts from one individual, summarized all known probands' clinical, molecular, and biochemical features and compared them, also to other metabolic forms of cutis laxa. We identified novel missense and the first nonsense variant strongly affecting ATP6V1A expression. All six ARCL2D affected individuals show equally severe cutis laxa and dysmorphism at birth. While for one no information was available, two died in infancy and three are now adolescents with mild or absent intellectual disability. Muscular weakness, ptosis, contractures, and elevated muscle enzymes indicated a persistent myopathy. In cellular studies, a fragmented Golgi compartment, a delayed Brefeldin A‐induced retrograde transport and glycosylation abnormalities were present in fibroblasts from two individuals. This is the second and confirmatory report on pathogenic variants in ATP6V1A as the cause of this extremely rare condition and the first to describe a nonsense allele. Our data highlight the tremendous clinical variability of ATP6V1A related phenotypes even within the same family.

Overview of the Pulmonary Manifestations in Patients with Autosomal Recessive Cutis Laxa Type IC.

Background: Autosomal recessive cutis laxa type IC (ARCL1C) is characterized by cutis laxa accompanied by pulmonary, gastrointestinal, urinary, musculoskeletal involvement caused by biallelic mutations in latent transforming growth factor-beta binding protein 4 (LTBP4) gene. The overall prognosis is poor, and most patients die in infancy because of severe pulmonary emphysema (PE). Aim: We aimed to evaluate 3 ARCL1C patients, 2 of whom are still alive and in their childhood period, from 2 unrelated families with novel LTBP4 mutations, to demonstrate the clinical variability of pulmonary involvement. Materials and Methods: Three children who were molecularly confirmed by LTBP4 sequencing analysis were comprehensively reviewed in terms of pulmonary manifestations through chest examination, lung function tests (LFTs), chest X-ray, and thorax computed tomography. Results: Family 1 (c.3740A>G LTBP4 mutation): A 5-year-old male patient with pulmonary artery stenosis (PAS) presented with persistent cough and exhibited mild restriction on LFT. Family 2 (c.2T>G LTBP4 mutation): Radiographic examinations revealed PE in a 7-year-old female patient who was operated for diaphragmatic hernia. She had recurrent bronchiolitis and pulmonary infections. LFT revealed both obstructive and restrictive pattern. Her cousin also had respiratory distress with the onset of the newborn period and died due to bilateral pneumothorax in early infancy. Conclusion: The variable severity of pulmonary findings was shown in these patients. It should also be kept in mind that there could be intrafamilial variability of systemic manifestations. Although obstructive lung disease is expected to be seen in ARLC1C patients, restrictive LFT patterns may also be detected as a result of comorbidities such as diaphragmatic hernia and PAS.

Whole Exome Sequencing Identifies a Homozygous PYCR1 Missense Variant in a Patient with Autosomal Recessive Cutis Laxa Type 2B: A Case Report

: Autosomal recessive cutis laxa type 2B (ARCL2B) is a rare genetic connective tissue disorder characterized by wrinkled inelastic skin, intellectual disability, growth retardation, developmental delay, skeletal abnormalities, and facial dysmorphism. Recently, PYCR1, encoding the pyrroline-5-carboxylate reductase 1, was reported as the first gene involved in ARCL2B. In this study, using whole exome sequencing, we identified a homozygous PYCR1 missense mutation, c.722C>A; p.Ala241Asp, in an Iranian male patient. Our report expands the clinical spectrum of PYCR1 mutations. Furthermore, this study shows that whole exome sequencing could serve as a viable diagnostic approach to identify the etiology of rare genetic diseases.

Autosomal recessive cutis laxa: a novel mutation in the FBLN5 gene in a family.

FBLN5-related cutis laxa (CL) is a rare syndrome that can be inherited in an autosomal dominant or recessive manner. Autosomal recessive cutis laxa (ARCL), type IA, has been reported to be more severe. The disease is characterized by microcephaly, sagging cheeks, loose, wrinkled and redundant skin, emphysema, aorta or pulmonary artery abnormalities, inguinal hernia, and anomalies of internal organs. Homozygous mutations in the FBLN5 gene are responsible for the clinical manifestations. We report a family study of a child with ARCL. FBLN5 genes of the patient and parents were sequenced using next-generation sequencing technologies. Analyses showed that the patient was homozygous for the novel c.518A>G, p.R173H mutation in exon 6 of the FBLN5 gene, whereas the parents were heterozygous. The mutation was found to be 'possibly pathogenic' in bioinformatic analysis. We identified a novel FBLN5 mutation in a CL patient; pedigree and parental genetic analyses suggested ARCL. Our results also suggest that the mutation analysis provides useful evidence to support the clinical diagnosis and define the inheritance mode of CL in an apparently sporadic case.

A Novel ATP6V0A2 Mutation Causing Recessive Cutis Laxa with Unusual Manifestations of Bleeding Diathesis and Defective Wound Healing

Objective:Autosomal recessive cutis laxa type IIA (ARCL2A) is a rare congenital disorder characterized by loose and elastic skin, growth and developmental delay, and skeletal anomalies. It is caused by biallelic mutations in ATP6V0A2. Those mutations lead to increased pH in secretory vesicles and thereby to impaired glycosyltransferase activity and organelle trafficking. We aimed to identify the genetic and molecular cause of the unexpected hematological findings in a Turkish family.Materials and Methods:We performed clinical, genetic, and histological analyses of a consanguineous family afflicted with wrinkled and loose skin, microcephaly, intellectual disability, cleft lip and palate, downslanting palpebral fissures, ectopia lentis, bleeding diathesis, and defective wound healing.Results:Linkage analysis using SNP genotype data yielded a maximal multipoint logarithm of odds score of 2.59 at 12q24.21-24.32. Exome sequence analysis for the proband led to the identification of novel homozygous frameshift c.2085_2088del (p.(Ser695Argfs*12)) in ATP6V0A2, within the linked region, in the two affected siblings.Conclusion:Our patients do not have gross structural brain defects besides microcephaly, strabismus, myopia, and growth or developmental delay. Large platelets were observed in the patients and unusual electron-dense intracytoplasmic inclusions in fibroblasts and epidermal basal cells were observed in both affected and unaffected family members. The patients do not have any genetic defect in the VWF gene but von Willebrand factor activity to antigen ratios were low. Clinical findings of bleeding diathesis and defective wound healing have not been reported in ARCL2A and hence our findings expand the phenotypic spectrum of the disease.

Clinical and genetic analysis of a patient with cutis laxa

OBJECTIVE To identify potential mutation in a patient with cutis laxa through exome sequencing of genetic disease-related genes and explore its clinical and genetic features. METHODS Clinical data was collected for the proband and her parents. Exome sequencing was carried out on the proband. Suspected mutations were verified by Sanger sequencing. RESULTS Exome sequencing identified a compound heterozygous mutation of the ATP6V0A2 gene, c.187C>T (p.R63X) and c.1189G>C (p.A397P), in the proband. The mutations were respectively inherited from the father and mother. The patient was diagnosed with autosomal recessive cutis laxa type 2A (ARCL2A). CONCLUSION A case with ARCL2A was diagnosed. The novel mutation has expanded the spectrum of ATP6V0A2 mutations. Exome sequencing is a useful tool for the diagnosis of complex genetic diseases.

Autosomal recessive cutis laxa type-1 with complex systemic manifestations

Cutis laxa (CL) is a rare connective tissue disorder characterized by loose, sagging, and redundant skin. Both inherited and acquired forms are known. A 7-year-old boy, presented with loose, sagging skin chiefly over the face, extremities, and skin folds since birth with recurrent respiratory and systemic complaints. The patient had a characteristic senile bloodhound appearance. Chest X-ray findings included emphysema, bronchopneumonia, and pulmonary hypertension. Ultrasonographic examination showed cystitis and bladder diverticula. Two-dimensional echocardiography showed primary pulmonary hypertension. Histopathological examination with Verhoeff-Van-Gieson stain showed markedly reduced elastic fibers. Serum amino acids, copper, and ceruloplasmin were normal. About sixty cases of autosomal recessive cutis laxa type 1 (ARCL-1) have been reported in literature. There is no definitive treatment available at present, and symptomatic management is the mainstay of treatment. Differential diagnosis includes Ehlers–Danlos syndrome, congenital disorders of glycosylation syndrome, and pseudoxanthoma elasticum. We report this case of ARCL-1 for its rarity and complex systemic involvement.

A Transcriptome Study of Progeroid Neurocutaneous Syndrome Reveals POSTN As a New Element in Proline Metabolic Disorder.

Aging is a complex biological process. A study of pyrroline-5-carboxylate reductase 1 (PYCR1) deficiency, which causes a progeroid syndrome, may not only shed light on its genetic contribution to autosomal recessive cutis laxa (ARCL) but also help elucidate the functional mechanisms associated with aging. In this study, we used RNA-Seq technology to examine gene expression changes in primary skin fibroblasts from healthy controls and patients with PYCR1 mutations. Approximately 22 and 32 candidate genes were found to be up- and downregulated, respectively, in fibroblasts from patients. Among the downregulated candidates in fibroblasts with PYCR1 mutations, a strong reduction in the expression of 17 genes (53.1%) which protein products are localized in the extracellular space was detected. These proteins included several important ECM components, periostin (POSTN), elastin (ELN), and decorin (DCN); genetic mutations in these proteins are associated with different phenotypes of aging, such as cutis laxa and joint and dermal manifestations. The differential expression of ten selected extracellular space genes was further validated using quantitative RT-PCR. Ingenuity Pathway Analysis revealed that some of the affected genes may be associated with cardiovascular system development and function, dermatological diseases and conditions, and cardiovascular disease. POSTN, one of the most downregulated gene candidates in affected individuals, is a matricellular protein with pivotal functions in heart valvulogenesis, skin wound healing, and brain development. Perturbation of PYCR1 expression revealed that it is positively correlated with the POSTN levels. Taken together, POSTN might be one of the key molecules that deserves further investigation for its role in this progeroid neurocutaneous syndrome.

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.