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

Abstract

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.

Introduction

Cutis laxa (CL) is a group of connective tissue disorders characterized by loose and/or wrinkled skin that presents with a prematurely aged appearance. CL can also affect other parts of the body, including the heart, blood vessels, joints, intestines, and lungs. Several forms of CL have been described with different patterns of inheritance: autosomal dominant, autosomal recessive, or X-linked. Compared with other types of CL,^1,2 mutations in elastin (ELN), fibulin 4 (FBLN4), fibulin 5 (FBLN5), and latent transforming growth factor-beta binding protein 4 (LTBP4) genes are known to cause CL-related syndromes that are more often associated with respiratory complications, such as tracheobronchomalacia, recurrent lung infections, bronchiectasis, and pulmonary emphysema (PE).

Autosomal recessive CL type IC (ARCL1C) also known as Urban–Rifkin–Davis syndrome is caused by homozygous or compound heterozygous mutations in the LTBP4 gene (OMIM: 613177). It was first described by Urban et al. through 4 unrelated patients who had severe respiratory distress, with cystic and atelectatic changes in the lungs, complicated by tracheomalacia and diaphragmatic hernia, which were accompanied by gastrointestinal, urinary, musculoskeletal, craniofacial, and dermal involvement.³ Following these cases, 17 additional patients with LTBP4-related CL from 11 unrelated families have been reported up to date, almost all of whom were deceased owing to PE in the early infantile period.^4,5

This study aims to present and 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 patients diagnosed with ARCL1C were comprehensively reviewed in terms of pulmonary manifestations. All patients were examined by a specialist in pediatric pulmonology. Lung function measurements including forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), FEV1/FVC, forced expiratory flow between 25% and 75% of FVC, through electronic spirometer was performed according to the European Respiratory Society and ATS guidelines. Lung function was measured before and 15 min after the administration of salbutamol to measure the reversibility of obstruction. The change in FEV1 > 12% as a percentage on the baseline values and/or increase in absolute volume >200 mL have been defined as reversible obstruction according to these guidelines. The chest X-rays and thorax computed tomography (CT) were assessed by a pediatric radiology specialist. Informed consent was obtained from the parents to use the patients' clinical data and photographs.

Genetic Analysis

Family 1

All coding exons and the corresponding exon–intron boundaries of the LTBP4 gene were sequenced and the homozygous c.3740A>G, p.N1247S mutation was identified (Ensembl Transcript: ENST00000396819). This variant was classified as a disease-causing novel mutation according to prediction databases and the American College of Medical Genetics and Genomics (ACMG) classification criteria (7 pathogenic predictions from DANN, EIGEN, FATHMM-MKL, M-CAP, MutationTaster, PrimateAI and REVEL versus 2 benign predictions from DEOGEN2 and SIFT). Segregation analysis revealed that both the father and mother were heterozygous carriers of this mutation.

Family 2

Clinical exome study (TruSight/Illumina) revealed c.2T>G, p.M1R homozygous mutation in LTBP4 gene in patient 2 (Ensembl Transcript: ENST00000396819). This variant was classified as a disease-causing novel mutation according to prediction databases ACMG classification criteria. (This variant was identified as pathogenic since 5 pathogenic predictions from EIGEN, FATHMM-MKL, M-CAP, MutationTaster, and SIFT versus 1 benign prediction from DANN.) Confirmation analysis of this novel mutation was performed using Sanger sequencing. The c.2T>G, p.M1R homozygous mutation was detected by directly sequencing intron 4 and exon 5 of LTBP4 gene in patient 3.

Clinical Characteristics of the Patients

Family 1

A 5-year-old male patient (patient 1) was referred to the Pediatric Genetic clinic with a history of pulmonary artery stenosis (PAS) surgery and biotinidase deficiency. He was born at full-term (weight 3,400 g) to consanguineous parents (first cousins). PAS was detected postnatally; hence, he underwent surgery a year previously. He has been taking biotin supplements owing to biotinidase deficiency since birth. He achieved all the developmental milestones on time. He has been suffering from a chronic cough. He had a history of recurrent bronchitis and pneumonia requiring oral antibiotic treatment once. There was no similar case in the family. On physical examination, his weight was 20 kg (50th P), height 113 cm (50th P), and occipitofrontal diameter (OFD) 48 cm (−2 standard deviation [SD]). He had epicanthus, long philtrum, puffiness on periorbital area and cheeks, prominent ears, and thin upper lip (Fig. 1). Loose and inelastic skin was more noticeable on anterior abdominal wall skin while seated. A moderate joint hyperlaxity was also noted. Abdominal ultrasonography did not reveal any pathologic findings.

FIG. 1.

Patient 1: puffy appearance in the periorbital area and cheeks; loose and inelastic skin on the anterior abdominal wall.

Lung function test (LFT) exhibited mild restriction (Table 1). He had no response to the administration of a bronchodilator. Chest X-ray showed an increase in the aeration of bilateral hemithorax, heterogeneous radiolucency of the lung fields, and flattened hemidiaphragm (Fig. 2). Thorax CT revealed a linear fibrotic band extending to the pleura on the right middle lobe, lingula, and left lower lobe, which is not specific to the disease.

Table 1.

Summary of the Respiratory System Examinations

Patient	Age	Chief complaint	Clinical manifestation	Lung function test				Chest imaging
				FEV1 % (L)	FVC % (L)	FEV1/FVC %	FEF 25–75 (L/)s	X-ray	CT
1	5 Years	Persistent cough	Recurrent bronchiolitis	83 (1.01)	76 (1.09)	107	75 (1.25)	PE-like	Nonspecific
2	7 Years	Chronic cough and sputum	Recurrent bronchiolitis and pulmonary infections	28 (0.43)	32 (0.57)	90	35 (0.73)	PE	Unilateral paraseptal bulla formation
3	58 Days	Abnormal breathing pattern and cyanosis	Respiratory distress	—				Pneumothorax	Bilateral parenchymal bulla formations

CT, computed tomography; FEF25–75, forced expiratory flow between 25% and 75% of FVC; FEV1, forced expiratory volume in the first second; FVC, forced vital capacity; PE, pulmonary emphysema.

FIG. 2.

Chest X-ray of patient 1 (5 years old) exhibits an increase in aeration of bilateral hemithorax, heterogeneous radiolucency of the lung fields, flattened hemidiaphragm, widened intercostal spaces, and sternal metallic sutures from previous surgery.

Family 2

A 7-years-old female patient (patient 2) was consulted owing to her dysmorphic facial appearance. She had a history of recurrent bronchitis. She was born at full-term to consanguineous parents (first cousins). A loose skin had been noticed at birth. She underwent surgery for diaphragmatic hernia on her 22nd day (the details about the operation were not noted). She suffered from chronic, persistent cough with recurrent hospitalizations owing to lung infections, especially during the winter season. She was able to walk independently by the age of 1 and speak 2-word phrases by 24 months of age. She had previously been operated for bilateral entropion and under-eye bags. Her weight was 20 kg (25–50th P), height 113 cm (25–50th P), and OFD 49 cm (−2 SD-mean). She had aged facial appearance. Physical examination showed down slanting palpebral fissures, puffy eyelids, droopy face, prominent ears, joint hyperlaxity, and severe sagging and inelastic skin, especially on the abdominal region (Fig. 3A). Mitral valve insufficiency (MVP) and enlargement of left cardiac compartments were detected on echocardiographic examination. Abdominal ultrasonography revealed a 12 mm diverticulum at the base of the bladder and mild dilatation of the bowel segments in the pelvic region. LFT exhibited severe restriction and obstruction (Table 1). She had no response to the administration of a bronchodilator. Chest X-ray revealed an increase in the aeration of bilateral hemithorax, widened intercostal spaces, heterogeneous radiolucency of the lung fields (Fig. 4A). Thorax CT revealed left paracardiac paraseptal lung bulla and displaced bronchovascular bundles (Fig. 4B).

FIG. 3.

(A) Patient 2: Downslanting palpebral fissures, puffy eyelids, droopy face, prominent ears, and severe sagging and inelastic skin. (B, C) Patient 3: A lax and redundant skin on nuchal area and abdomen.

FIG. 4.

(A) Chest X-rays of patient 2 (7 years old) exhibit increase in aeration of bilateral hemithorax, widened intercostal spaces, heterogeneous radiolucency of the lung fields, contour irregularity of paracardiac vascular structures, blunting of costophrenic angles, flattened left hemidiaphragm, irregularly shaped right hemidiaphragm and accompanying right basal heterogeneous opacities. (B) Axial thorax CT of lung demonstrates left paracardiac, paraseptal bulla, and displaced bronchovascular bundles. Radiodensity measurements of the bulla and lung parenchyma. Axial thorax CT of lung demonstrates left paracardiac paraseptal bulla and displaced bronchovascular bundles. CT, computed tomography.

Patient 3—the first cousin of patient 2—was born at 38th gestational week to consanguineous parents (first cousins). Abnormal breathing pattern was noticed since birth. Cyanosis following crying became visible after the 40th day; therefore, she was referred to pediatric cardiology. Echocardiography showed mild aortic and mitral valve insufficiency, patent foramen ovale. She was intubated and admitted to the pediatric intensive care unit because of the respiratory arrest during a cardiac examination. Pneumothorax was detected on the right lung and a chest tube was inserted. The patient was consulted to the Pediatric Genetic clinic at 48 days of age due to having a cousin with CL. Physical examination indicated puffy eyelids and lax-redundant skin that was evident in the nuchal area and abdomen (Fig. 3B, C). On the 3rd day of hospitalization, thorax tomography sections showing upper lobes, revealed right pneumothorax owing to the rupture of medial paraseptal lung bulla (Fig. 5). On the 6th day of hospitalization, she died as a result of severe bilateral pneumothorax.

FIG. 5.

(A) Chest X-ray of 12-day-old patient 3 exhibits right pneumothorax during the expiratory phase (black open arrows). The hemidiaphragm is elevated, ribs are parallel to each other, intercostal spaces are narrowed. Heart and mediastinum are shifted to the left. (B) Axial thorax CT of patient 3 (51 days old) demonstrates right pneumothorax owing to the rupture of medial paraseptal lung bulla (white open arrow). Midline structures are shifted to the left. Radiodensity measurements of the bulla formations (white arrowheads), lung parenchyma (black arrowhead), and air in the pleural space. Axial thorax CT of lung patient 3 (51 days old) demonstrates right pneumothorax owing to the rupture of medial paraseptal lung bulla. Midline structures are shifted to the left. Notice other parenchymal bulla formations (white open arrows).

Discussion

Latent transforming growth factor-beta-binding proteins are located in the extracellular matrix and serve as molecular modulators for the disposition of transforming growth factor-beta (TGF-β) and the assembly of other matrix proteins.⁶ ELN is an important component of the extracellular matrix that is required to maintain the integrity of lung parenchyma and small airways. PE involves in the loss of elasticity and enlargement of the air sacs in the lungs. Severely reduced expression of LTBP4 reveals significant disruption of elastic fibers in multiple tissues and causes a severe PE-like condition associated with cardiomyopathy in transgenic mice.⁷ At the molecular level, these abnormalities are correlated with fragmented, disintegrated elastic fibers, and abnormal TGF deposition in the extracellular space as a consequence of defective TGF signaling.⁸ Furthermore, postmortem histology of the lung reveals severe septation defects, extreme airspace enlargement, collapsed parenchyma, and airways in LTBP4-deficient patients.³

The overall prognosis is poor, with a mortality rate of 72% and the mean age of death at 2.4 years (median age 6 months) in LTBP4-related CL.⁹ Emphysematous changes are the main reason for fatal respiratory complications. PE is a type of chronic obstructive pulmonary disease and the obstructive pattern is an expected finding in LFT. Patient 1 was suffering (mostly during winter) from chronic, persistent, nonpurulent cough with mild bronchial reactive airway attacks. Hyperaeration was seen on a chest X-ray. However, his repeated LFTs exhibited a restrictive pattern. There was no evidence of tracheobronchomalacia. As mentioned previously, he had a history of PAS surgery, which could be the reason for having a restrictive pattern. On the contrary, severe restrictive and obstructive lung functions with PE were detected at the age of 6 in patient 2. She had MVP with enlargement of left cardiac compartments. A mixed obstructive and restrictive pattern of this case could be attributed to the concomitant diaphragmatic hernia. There has been only 1 reported female patient with LFT results who has been able to survive, up to the age of 23.⁴ There was no evidence of other organ involvements except mild MVP. PE was mild upon CT evaluation, but her LFT showed severe obstructive lung disease with FEV1/FVC of 41% (50% after bronchodilation).

The majority of the currently described LTBP4 pathogenic variants are frameshift, nonsense, and splice variants resulting in a premature termination codon and activation of the nonsense-mediated messenger RNA (mRNA) decay.⁹ Moreover, few missense variants have been also reported, which causes the loss of one of the highly conserved cysteine residues located in a TB or hybrid domain. The genotype–phenotype correlation can be established, based on the assumption that all the severe fatal or fatal cases in the infancy are the result of mutations in one of the hybrid or TB domains.^3,4 The c.2377_2378insA, c.3856T>A p.G793Efs*5, and p.C1286S compound heterozygous mutation that is affecting the EGF-like domains, has been identified in the 23-year-old patient with mild PE. Patient 1 who had c.3740A>G LTBP4 missense mutation located on exon 28 affecting the EGF-like calcium-binding domain, demonstrated primarily PAS, mild CL, and PE-like findings.

An intronic c.2T>G mutation causing the coding impact of protein start loss predicted to cause truncation of TB domain was identified in family 2. Although presence of intrafamilial clinical variability of skin and other systemic manifestations are in support of dominantly inherited CL, family 2 demonstrated variability of clinical findings. Patient 2, presented severe CL, diaphragmatic hernia, emphysematous changes with localized paraseptal bullous lesion on the left lung, whereas patient 3 had respiratory distress with the onset of the newborn period. Her CL was less severe and there was no diaphragm hernia, either. She had diffused paraseptal and parenchymal bulla formations that caused pneumothorax and consequently early death. The common features of these 2 patients from the same family were the presence of severe pulmonary findings and no cardiac defect, which supports the predicted genotype–phenotype correlation.

Conclusion

Few patients reported with ARCL1C, almost all of whom have had severe pulmonary complications. 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. It should also be kept in mind that there could be intrafamilial variability of systemic manifestations. LTBP-related CLs should be followed up regularly to prevent life-threatening complications.

Authors' Contributions

All authors contributed extensively to the work presented in this article. All authors have contributed significantly to the conception, design, or acquisition of data, or analysis and interpretation of data; drafting/revising the article for important intellectual content; and approval of the final version to be published.

Author Disclosure Statement

All the authors declare that there is not any conflict of interest.

Funding Information

There is no funding source.