Rare variants in alpha 1 antitrypsin deficiency: a systematic literature review

BACKGROUND

Alpha 1 Antitrypsin Deficiency (AATD) is a largely underrecognized genetic condition characterized by low Alpha 1 Antitrypsin (AAT) serum levels, resulting from variations in SERPINA1. Many individuals affected by AATD are thought to be undiagnosed, leading to poor patient outcomes. The Z (c.1096G > A; p.Glu366Lys) and S (c.863A > T; p.Glu288Val) deficiency variants are the most frequently found variants in AATD, with the Z variant present in most individuals diagnosed with AATD. However, there are many other less frequent variants known to contribute to lung and/or liver disease in AATD. To identify the most common rare variants associated with AATD, we conducted a systematic literature review with the aim of assessing AATD variation patterns across the world.

METHODS

A systematic literature search was performed to identify published studies reporting AATD/SERPINA1 variants. Study eligibility was assessed for the potential to contain relevant information, with quality assessment and data extraction performed on studies meeting all eligibility criteria. AATD variants were grouped by variant type and linked to the geographical region identified from the reporting article.

RESULTS

Of the 4945 articles identified by the search string, 864 contained useful information for this study. Most articles came from the United States, followed by the United Kingdom, Germany, Spain, and Italy. Collectively, the articles identified a total of 7631 rare variants and 216 types of rare variant across 80 counties. The F (c.739C > T; p.Arg247Cys) variant was identified 1,281 times and was the most reported known rare variant worldwide, followed by the I (c.187C > T; p.Arg63Cys) variant. Worldwide, there were 1492 Null/rare variants that were unidentified at the time of source article publication and 75 rare novel variants reported only once.

CONCLUSION

AATD goes far beyond the Z and S variants, suggesting there may be widespread underdiagnosis of patients with the condition. Each geographical region has its own distinctive variety of AATD variants and, therefore, comprehensive testing is needed to fully understand the true number and type of variants that exist. Comprehensive testing is also needed to ensure accurate diagnosis, optimize treatment strategies, and improve outcomes for patients with AATD.

Baseline characteristics from a 3-year longitudinal study to phenotype subjects with COPD: the FOOTPRINTS study

BACKGROUND

FOOTPRINTS® is a prospective, longitudinal, 3-year study assessing the association between biomarkers of inflammation/lung tissue destruction and chronic obstructive pulmonary disease (COPD) severity and progression in ex-smokers with mild-to-severe COPD. Here, we present baseline characteristics and select biomarkers of study subjects.

METHODS

The methodology of FOOTPRINTS® has been published previously. The study population included ex-smokers with a range of COPD severities (Global Initiative for Chronic Obstructive Lung Disease [GOLD] stages 1-3), ex-smokers with COPD and alpha-1-antitrypsin deficiency (A1ATD) and a control group of ex-smokers without airflow limitation (EwAL). At study entry, data were collected for: demographics, disease characteristics, history of comorbidities and COPD exacerbations, symptoms, lung function and volume, exercise capacity, soluble biomarkers, and quantitative and qualitative computed tomography. Baseline data are presented with descriptive statistical comparisons for soluble biomarkers in the individual GOLD and A1ATD groups versus EwAL.

RESULTS

In total, 463 subjects were enrolled. The per-protocol set comprised 456 subjects, mostly male (64.5%). The mean (standard deviation) age was 60.7 (6.9) years. At baseline, increasing pulmonary symptoms, worse lung function, increased residual volume, reduced diffusing capacity of the lung for carbon monoxide (DLco) and greater prevalence of centrilobular emphysema were observed with increasing disease severity amongst GOLD 1-3 subjects. Subjects with A1ATD (n = 19) had similar lung function parameters to GOLD 2-3 subjects, a high residual volume comparable to GOLD 3 subjects, and similar air trapping to GOLD 2 subjects. Compared with EwAL (n = 61), subjects with A1ATD had worse lung function, increased residual volume, reduced DLco, and a greater prevalence of confluent or advanced destructive emphysema. The soluble inflammatory biomarkers white blood cell count, fibrinogen, high-sensitivity C-reactive protein and plasma surfactant protein were higher in GOLD 1-3 groups than in the EwAL group. Interleukin-6 was expressed less often in EwAL subjects compared with subjects in the GOLD and A1ATD groups. Soluble receptor for advanced glycation end product was lowest in GOLD 3 subjects, indicative of more severe emphysema.

CONCLUSIONS

These findings provide context for upcoming results from FOOTPRINTS®, which aims to establish correlations between biomarkers and disease progression in a representative COPD population.

TRIAL REGISTRATION NUMBER

NCT02719184, study start date 13/04/2016.

Distribution of the Clinical Manifestations of Alpha 1 Antitrypsin Deficiency in Respiratory Outpatients from an Area of Northern Italy

BACKGROUND

Alpha 1 antitrypsin deficiency (AATD) is an autosomal codominant genetic condition that affects Caucasians of the European population due to the presence of a deficient allele of the SERPINA1 gene. A frequency of about 1/5,000 individuals has been estimated in Italy.

OBJECTIVES

The aim of the study was to evaluate the distribution of the clinical manifestations of severe and intermediate genetic AATD in the geographic area around Parma in Northern Italy.

METHOD

238 subjects were submitted to molecular analysis of the SERPINA1 gene, and data on anthropometric variables, smoking habits, number of packs per year, AAT serum concentration, and clinical manifestations were recorded and presented as mean ± SD or median values (1st quartile; 3rd quartile).

RESULTS

The results show a distribution of genetic AATD of 4.1% of the screened population in the area encompassing the city of Parma. PI*MS and PI*MZ were the most common genotypes at 40.9% and 28.2% of the population with genetic AATD, and asthma and emphysema were the most represented clinical manifestations.

CONCLUSION

Our study allowed to increase the knowledge of the distribution of genetic AATD in Northern Italy providing information regarding frequencies of genotypes and clinical manifestations of the disorder.

Recurrence of emphysema post-lung transplantation in a patient with alpha 1 antitrypsin deficiency (AATD)

The genetic disorder alpha 1 antitrypsin deficiency (AATD) results in reduced levels of alpha 1 antitrypsin (AAT) in the lung and an imbalance between AAT anti-protease activity and the activity of proteases that degrade elastin and connective tissues. This imbalance commonly leads to the excessive proteolysis of structural tissue of the alveoli, causing chronic obstructive pulmonary disease (COPD)/emphysema. While patients with AATD are encouraged to make lifestyle changes, including stopping smoking, and can be treated with alpha 1 antitrypsin therapy (AAT therapy) to slow progression of COPD/emphysema, damage to the lungs is irreparable, and therefore, lung transplantation is required in severe cases. However, following lung transplant, the genetic cause of AATD-related COPD/emphysema remains, and patients may continue to be at risk of redeveloping COPD/emphysema.

Recurrence of COPD/emphysema was observed in a patient with AATD 2 years after initial successful lung transplantation and cessation of AAT therapy who recommenced smoking after no signs of disease at the 1-year assessment. This case demonstrates that smoking cessation is critical in patients with AATD, even after lung transplant, and it highlights that patients with AATD may benefit from AAT therapy post-lung transplant.

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Patients with AATD can redevelop emphysema following lung transplantation.

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Abstinence from smoking remains crucial in all patients with AATD.

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AAT therapy may be required in patients who redevelop emphysema post-lung transplant.

The importance of effective registries in pulmonary diseases and how to optimize their output

Randomized controlled trials (RCTs) are essential for the approval of new therapies; however, because of their design, they provide little insight concerning disease epidemiology/etiology and current clinical practice. Particularly, in lung disease, rigid inclusion/exclusion criteria can limit the generalizability of pivotal trial data. Noninterventional studies (NIS), conducted through the well-established mechanism of patient registries, are undervalued as a means to close data gaps left by RCTs by providing essential data that can guide patient care at different levels from clinical decision-making to health-care policy. While NIS contribute valuable data in all disease areas, their importance in rare diseases cannot be underestimated. In respiratory disease, registries have been essential in understanding the natural history and different phenotypes of rare conditions, such as alpha 1 antitrypsin deficiency, cystic fibrosis, and idiopathic pulmonary fibrosis. Importantly, additional therapeutic outcome data were generated. While measures for enhancing data quality in RCTs have evolved significantly, the approach and effectiveness of registries is variable. Within this article, we review the contribution of registries to pulmonary disease and make recommendations for their effective management. Additionally, we assess limitations of registry data as well as challenges to registry operation, including the impact of the European Union General Data Protection Regulation.

Alpha 1 antitrypsin distribution in an allergic asthmatic population sensitized to house dust mites

Background and objective

Severe alpha1 antitrypsin deficiency has been clearly associated with pulmonary emphysema, but its relationship with bronchial asthma remains controversial. Some deficient alpha 1 antitrypsin (AAT) genotypes seem to be associated with asthma development. The objective of this study was to analyze the distribution of AAT genotypes in asthmatic patients allergic to house dust mites (HDM), and to asses a possible association between these genotypes and severe asthma.

Methods

A cross-sectional cohort study of 648 patients with HDM allergic asthma was carried out. Demographic, clinical and analytical variables were collected. PI*S and PI*Z AAT deficient alleles of the SERPINA1 gene were assayed by real-time PCR.

Results

Asthma was intermittent in 253 patients and persistent in 395 patients (246 mild, 101 moderate and 48 severe). One hundred and forty-five asthmatic patients (22.4%) with at least one mutated allele (S or Z) were identified. No association between the different genotypes and asthma severity was found. No significant differences in all clinical and functional tests, as well as nasal eosinophils, IgA and IgE serum levels were observed. Peripheral eosinophils were significantly lower in patients with the PI*MS genotype (p = 0.0228). Neither association between deficient AAT genotypes or serum ATT deficiency (AATD) and development of severe asthma, or correlation between ATT levels and FEV1 was observed.

Conclusion

In conclusion, the distribution of AAT genotypes in HDM allergic asthmatic patients did not differ from those found in Spanish population. Neither severe ATTD or deficient AAT genotypes appear to confer different clinical expression of asthma.

Free light chains: potential biomarker and predictor of mortality in alpha-1-antitrypsin deficiency and usual COPD

Background

Circulating free light chains (FLCs) can alter neutrophil migration, apoptosis and activation and may be a biomarker of autoimmune disease and adaptive immune system activation. These pathogenic roles could be relevant to lung disease in alpha 1 antitrypsin deficiency (A1ATD) and chronic obstructive pulmonary disease (COPD).

Methods

Total combined (c)FLCs were measured using the FreeLite® assay in 547 patients with A1ATD and 327 patients with usual COPD in the stable state, and assessed for association with clinical phenotype, disease severity, airway bacterial colonisation and mortality. Univariate and multivariate analyses were undertaken.

Results

Circulating cFLCs were static in the stable state when measured on 4 occasions in A1ATD and twice in usual COPD. Levels were inversely related to renal function (A1ATD and COPD p = <0.01), and higher in patients with chronic bronchitis (p = 0.019) and airway bacterial colonisation (p = 0.008). After adjusting for renal function and age the relationship between cFLCs and lung function was weak. Kaplan Meier curves showed that cFLC > normal (43.3 mg/L) significantly associated with mortality in both cohorts (A1ATD p = 0.001, COPD p = 0.013).

Conclusions

cFLCs may be a promising biomarker for risk stratification in A1ATD and COPD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0348-1) contains supplementary material, which is available to authorized users.