DEFI-ALFA: The French key to the alpha1 mystery?

Alpha-1-Antitrypsin Deficiency in Children-Unmet Needs Concerning the Liver Manifestation

OBJECTIVES

This study aimed to analyse the clinical course of 45 children with severe alpha-1-antitrypsin deficiency (AATD) registered in our clinic to detect possible predictors of poor outcomes.

METHODS

The clinical and biological data of 45 patients with homozygous or compound heterozygous AATD were analysed. The data were collected retrospectively going back to 2005 and prospectively from May 2020 until October 2021. It was based on questionnaires, laboratory values, sonography, and biopsy findings. Liver disease was classified into four grades depending on the grade of liver disease: mild or no liver disease, moderate disease, severe disease, and liver transplantation.

RESULTS

Thirty-nine patients (86.7%) had a Pi*ZZ and five (11.1%) a Pi*SZ genotype. One patient showed a new, not-yet-described compound heterozygous genotype (Pi*Z + Asp95Asn). A total of 66.7% of the cohort showed mild or no liver disease, 20% moderate, and 13.3% severe. AATD was diagnosed in most cases because of liver abnormalities, such as the elevation of transaminases (42.2%). A total of 29.4% of the patients with neonatal icterus prolongatus developed severe liver disease, and 25.7% were born small for their gestational age (SGA). Diseases of the atopic type were reported in 47.4% of the cases.

CONCLUSIONS

The presence of neonatal icterus prolongatus in the first weeks of life was significantly more likely in severe courses of liver disease (r = 0.371, p = 0.012). A tendency toward atopic comorbidity in AAT-deficient children needs to be further evaluated.

Alpha-1 antitrypsin deficiency: A re-surfacing adult liver disorder

Alpha-1 antitrypsin deficiency (AATD) arises from mutations in the SERPINA1 gene encoding alpha-1 antitrypsin (AAT) that lead to AAT retention in the endoplasmic reticulum of hepatocytes, causing proteotoxic liver injury and loss-of-function lung disease. The homozygous Pi∗Z mutation (Pi∗ZZ genotype) is responsible for the majority of severe AATD cases and can precipitate both paediatric and adult liver diseases, while the heterozygous Pi∗Z mutation (Pi∗MZ genotype) is an established genetic modifier of liver disease. We review genotype-related hepatic phenotypes/disease predispositions. We also describe the mechanisms and factors promoting the development of liver disease, as well as approaches to evaluate the extent of liver fibrosis. Finally, we discuss emerging diagnostic and therapeutic approaches for the clinical management of this often neglected disorder.

[Alpha-1 antitrypsin deficiency: cause and cofactor for liver disease]

Alpha-1-antitrypsin deficiency (AATD) is a genetic disorder arising due to mutation in alpha1-antitrypsin (AAT). AAT mutations interfere with the AAT production/secretion, cause decreased AAT serum levels and accumulation of AAT in the liver. The excess AAT leads to a proteotoxic liver disease, while the lack of AAT in systemic circulation predisposes to lung injury. While AATD related lung disease is well understood, liver disease needs further awareness. Non-invasive liver stiffness measurement constitutes a useful method to estimate the extent of liver fibrosis. Significant liver fibrosis occurs in 20-35 % of individuals with the classic, severe genotype Pi*ZZ. Genotype Pi*SZ, also known as the compound heterozygous form, confers an increased risk of both liver fibrosis and liver neoplasia. Even the heterozygous genotype Pi*MZ increases the odds of fibrosis in presence of further risk factors such as obesity, male sex, metabolic syndrome and diabetes mellitus. In individuals with non-alcoholic fatty liver disease or alcohol misuse it promotes the development of liver cirrhosis. While no drug treatment exists for AATD-related liver disease, there are several compounds in clinical phase II/III-trials. These either silence the AAT production via siRNA or facilitate the secretion of AAT from the liver due to an improved folding.

Utility of Transient Elastography for the Screening of Liver Disease in Patients with Alpha1-Antitrypsin Deficiency

Screening of liver disease in alpha-1 antitrypsin deficiency (AATD) is usually carried out with liver enzymes, with low sensitivity. We conducted a multicenter cross-sectional study aiming to describe the utility of transient elastography for the identification of liver disease in patients with AATD. A total of 148 AATD patients were included. Among these, 54.7% were Pi*ZZ and 45.3% were heterozygous for the Z allele. Between 4.9% and 16.5% of patients had abnormal liver enzymes, without differences among genotypes. Liver stiffness measurement (LSM) was significantly higher in Pi*ZZ individuals than in heterozygous Z (5.6 vs. 4.6 kPa; p = 0.001). In total, in 8 (5%) individuals LSM was >7.5 kPa, considered significant liver fibrosis, and ≥10 kPa in 3 (1.9%) all being Pi*ZZ. Elevated liver enzymes were more frequently observed in patients with LSM > 7.5 kPa, but in 5 out of 8 of these patients all liver enzymes were within normal range. In patients with AATD, the presence of abnormal liver enzymes is frequent; however, most of these patients do not present significant liver fibrosis. Transient elastography can help to identify patients with liver fibrosis even with normal liver enzymes and should be performed in all Z-allele carriers to screen for liver disease.

Non-Invasive Assessment and Management of Liver Involvement in Adults With Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin deficiency (AATD) is a systemic disorder affecting mainly the lung and the liver and is caused by mutations in SERPINA1, the AAT gene. A homozygous "Pi*Z" mutation (Pi*ZZ genotype) may cause liver fibrosis on its own independently of pulmonary AATD manifestation, while heterozygous Pi*Z carriage (Pi*MZ genotype) is considered a strong risk factor for development of liver cirrhosis in patients with concomitant liver disease such as alcoholic and non-alcoholic liver disease. In Pi*ZZ homozygotes, liver disease constitutes the second leading cause of death and is highly heterogeneous. About 35% of Pi*ZZ individuals display significant liver fibrosis on biopsy (i.e., fibrosis stage ≥ 2 on scale 0-4). Among non-invasive methods for liver fibrosis assessment, liver stiffness measurement (LSM) via vibration-controlled transient elastography (VCTE) has been most widely evaluated. Based on these data, Pi*ZZ adults have 20x increased odds of developing advanced liver fibrosis (i.e., fibrosis stage ≥ 3) than adults without AAT mutation. Risk factors for accelerated fibrosis progression are male sex, age ≥ 50 years, alcohol misuse, obesity, diabetes mellitus, or metabolic syndrome. Unlike VCTE, other ultrasound- and magnetic resonance-based elastography methods have been assessed in small cohorts of Pi*ZZ individuals and remain to be comprehensively validated. Among blood-based fibrosis tests, AST-to-platelet ratio index (APRI) correlates moderately with histologic fibrosis stage and LSM. Given APRI's wide availability, it can be used for risk stratification as an adjunct to LSM or when LSM is not at hand. Despite recent efforts, AATD-related liver disease, especially for genotypes other than Pi*ZZ, remains greatly understudied. AATD individuals should be offered liver biochemistry, liver ultrasound, and non-invasive fibrosis assessment at the time of diagnosis to detect potential complications and for proper risk stratification. If signs of AATD-related liver disease occur (i.e., pathologic fibrosis test or repeatedly elevated liver enzymes), patients should be referred to a health care center specialized in AATD-related liver disease and be screened for potentially treatable comorbidities. To exclude the latter, they may need a liver biopsy. Moreover, every health care provider of an AATD individual should be aware of the potential liver manifestation, counsel their patient on modifiable hepatic risk factors, and offer them regular liver check-ups.