Prevalence of alpha-1 antitrypsin high-risk variants in Mexican mestizo population and their association with lung function values.

INTRODUCTION: Chronic obstructive pulmonary disease (COPD) is characterized by restricted airflow. The best-documented genetic factor is alpha-1 antitrypsin (AAT). AAT is encoded by the SERPINA1 gene. The PiZ (rs28929474) and PiS (rs17580) variants are believed to cause severe AAT deficiency and are linked to a high risk of developing COPD. This study sought to identify whether genetic polymorphisms rs28929474 and rs17580 are associated with COPD susceptibility and lung function values in a Mexican mestizo population. METHODS: In this study, 558 smokers were included, of whom 279 had COPD and 279 did not (smokers without COPD - SWC). The PiS and PiZ variants were genotyped by allelic discrimination. Independent populations and lung function values were compared using the Kruskal-Wallis test. A bivariate logistic regression analysis was also conducted. RESULTS: Stage I and iv COPD patients showed significant differences in the frequencies of both heterozygous genotypes compared to SWC. For PiS, individuals with the heterozygous genotype AT demonstrated a decreased FEV1/FVC ratio compared to subjects with the homozygous genotype AA (P=0.037). A significant association was found between the FEV1/FVC ratio and genotype AA for PiS (OR=0.982, ß coefficient=-0.019, 95% CI=0.966-0.997). CONCLUSIONS: COPD-causing AAT deficiency risk alleles exist at a very low frequency among Mexican mestizo population. Although they are not directly linked in our study population with disease susceptibility, these risk alleles are associated with poorer lung function measurements. It is important to characterize how often these genetic risk variants occur in other Latin American populations.

[Genetic variants of alpha-1 antitrypsin: classification and clinical implications]. / Genetyczne warianty alfa-1 antytrypsyny ­ klasyfikacjai znaczenie kliniczne

Inherited alpha-1 antitrypsin deficiency is listed among the three most common genetic disorders in Caucasians. It considerably increases the risk of progressive obstructive lung diseases, mostly chronic obstructive pulmonary disease, as well as chronic liver disorders, hepatitis, cirrhosis, and cancer. It is estimated that more than 5.5% of the Polish population carries one of the most common deficiency phenotypes, which might be relatively easily detected due to low alpha-1 antitrypsin serum concentration. However, as well as being quantitative, alpha-1 antitrypsin deficiency might also be qualitative. These dysfunctional alpha-1 antitrypsin variants are characterized by scarce antiproteolytic activity and quite often by fully effective protein production resulting in normal serum levels. Consequently, dysfunctional variant identification is possible only by means of pheno- or genotyping. This review presents clinically useful characteristics of main genetic alpha-1 antitrypsin variants.

Ethnic differences in alpha-1 antitrypsin deficiency in the United States of America.

BACKGROUND: Our earlier publications have demonstrated that alpha-1 antitrypsin (AAT) deficiency is not a rare disorder in the United States with at least 33,728 PI*ZZ homozygote individuals at risk. METHOD: Using data on the prevalences of the two most common deficiency alleles PI*S and PI*Z in the five major individual ethnic subgroups in the United States, the numbers of heterozygotes for PI*MS and PI*MZ, and compound heterozygotes/homozygotes for PI*SS, PI*SZ and PI*ZZ have been determined for each ethnic subgroup. RESULTS: When the data for the prevalence of AAT deficiency in individual cohorts are displayed as a function of ethnic subgroup, striking differences are found in the numbers in each of the five phenotypic classes of PI*S and PI*Z. This type of analysis has demonstrated striking differences in the risk for AAT deficiency in each of these five ethnic subgroups. This analysis as a function of ethnic subgroup also has demonstrated that there are higher numbers of each of the five PI*S and PI*Z deficiency classes, namely PI*MS, PI*SS, PI*MZ, PI*SZ and PI*ZZ. CONCLUSIONS: This analysis has demonstrated that the highest risk for AAT deficiency is found in Whites, followed by Hispanics and Blacks with the lowest prevalence among Mexican Americans and no risk among Asians. The numbers for those at risk for AAT deficiency in the United States are well documented and in the present analysis there are, for example, a total of 48,904 PI*ZZ homozygotes at risk. The critical question for our healthcare professionals is 'When will the medical community acknowledge that AAT deficiency is a prevalent and well-documented human genetic disorder and develop appropriate mechanisms for early diagnosis, medical follow-up and treatment both in the United States and worldwide?'

alpha1-Antitrypsin deficiency is not an important cause of childhood liver diseases in a multi-ethnic Southeast Asian population.

AIM: We conducted a prospective study to determine the role of alpha1-antitrypsin (alpha1AT) deficiency in the pathogenesis of neonatal cholestasis and other childhood liver diseases in a multi-ethnic Southeast Asian population. METHODS: Prospective patients with neonatal cholestasis (group 1), other liver diseases (group 2) and children with other medical conditions (group 3) referred to the Paediatric Unit, University of Malaya Medical Centre, Malaysia, from May 2002 to June 2005, were screened for alpha1AT level and phenotype. alpha1AT level below 80 mg/dL was considered as low. RESULTS: Of the 114 patients (group 1, n = 53; group 2, n = 42; group 3, n = 19) screened, seven patients (6% of total; group 1, n = 1; group 2, n = 4; group 3, n = 2) had a alpha1AT level below 80 mg/dL. All had marginally low level (range 57-79 mg/dL), but none had a clinical diagnosis of alpha1AT deficiency. One patient had PiZ- heterozygous phenotype (alpha1AT level 217 mg/dL) while another patient had PiMS heterozygous. CONCLUSIONS: alpha1AT deficiency is not an important cause of neonatal cholestasis and childhood liver diseases in Malaysian children. In Malaysian children with neonatal cholestasis or other liver diseases, routine assay for alpha1AT phenotype is not recommended if there is no family history of neonatal cholestasis of uncertain aetiology, or if alpha1AT level is above 80 mg/dL.

Does the heterozygous state of alpha-1 antitrypsin deficiency have a role in chronic liver diseases? Interim results of a large case-control study.

BACKGROUND: The role of the heterozygous PiZ state of alpha-1 antitrypsin deficiency (alpha1ATD) in the pathogenesis of chronic liver disease (LD) is still a matter of controversy. AIM: To determine the prevalence of alpha1ATD heterozygote states in a large population of patients with established LD compared with individuals with no LD, and to determine whether the prevalence of PiZ is increased in patients with more severe LD. METHODS: A cross sectional case-control study among patients with and without LD. Blood samples were tested for alpha1AT levels and alpha1AT phenotype. The severity of LD was determined by clinical evaluation, lab tests, imaging studies and histopathology. RESULTS: In total, 1405 patients were enrolled; 651 with, and 754 without LD. Out of them, 173 patients had decompensated cirrhosis requiring liver transplantation. PiMZ was significantly more prevalent in White patients (3.5%) compared with Hispanics (1.7%; P = 0.029). There was no difference in PiMZ prevalence between the total LD group and the group with no LD (2.1% vs. 1.7%; P = 0.64). Within the LD group, 5.7% of 173 patients with decompensated LD, listed for liver transplantation, had PiMZ, compared with 2.1% of 478 patients with less severe LD (P = 0.016). Similarly, there was a disproportionately higher prevalence of PiZ among hepatitis C virus (HCV) patients (5.6%) and patients with nonalcoholic fatty liver disease (NAFLD) (5.0%) with decompensated LD, compared with HCV patients (1.2%) and NAFLD patients (1.9%) with less severe LD (P = 0.044 and 0.017, respectively). Patients with cryptogenic cirrhosis, who were not considered NAFLD patients, did not have a higher prevalence of PiMZ compared with patients with LD of known etiologies (1.9% vs. 2.3%; P = 0.12). CONCLUSIONS: We found no association between the heterozygous PiZ state of alpha1ATD and the presence of chronic LD in-general or the presence of cryptogenic cirrhosis. In contrast, patients with decompensated LD of any etiology had a significantly higher prevalence of PiMZ compared with patients with compensated LD. Furthermore, in patients with chronic LD due to HCV or NAFLD there was a significant association between the PiMZ heterozygous state and increased severity of LD and the need for liver transplantation. These interim results suggest that the PiMZ alpha1ATD heterozygous state may have a role in worsening LD due to HCV or NAFLD.