Highly variable clinical course in severe alpha 1-antitrypsin deficiency--use of polymerase chain reaction for the detection of rare deficiency alleles

Genome-environment interactions in the molecular pathogenesis of dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a heart muscle disease characterized by impaired contractility and dilation of the ventricles. In a subset of DCM patients, classical inheritance patterns occur (familial DCM), which have led to the identification of specific genomic loci and gene defects causing monogenic DCM subtypes. In the majority of DCM patients, however, there is no evidence for a monogenic etiology of the disorder (sporadic DCM), and in the absence of other recognizable etiological factors, these cases were classified as "idiopathic". Recent research suggests that cardiotropic viruses are important environmental factors in the pathogenesis of "idiopathic" cases and that DCM commonly results from interactions between genetic and environmental factors, whereas "pure" genetic forms are rather rare. Regarding genetics, the clinical cardiomyopathic phenotype associated with single gene defects may be highly variable for unknown reasons. Furthermore, a novel class of genetic defects was identified recently which provide a molecular basis for abnormal reactions of cardiomyocytes to environmental stress. These defects are paradigms of specific molecular links between genome and environment during the pathogenesis of DCM. Regarding environmental factors, a recent molecular virological study based on myocardial biopsies in a large series of sporadic DCM patients has detected cardiac viral infections in the majority of patients, with a broad spectrum of virus species being involved. Apparently, DCM does not only occur as a late sequela of acute viral myocarditis, but also in patients without clinical history of cardiac viral disease. Cardiotropic viruses thus emerge as prevalent environmental factors which may cause or influence the course of DCM in a large fraction of cases. Synopsis of current data suggests that a comprehensive picture of DCM pathogenesis can only be drawn if both genetic and environmental pathogenetic factors are considered. The course of cardiac viral infections depends strongly on genetic host factors and may range from rapid and complete virus elimination or silencing without clinical symptoms, to rapidly progressive or fatal disease. Viruses interact not only with genetically heterogenous host systems of virus uptake, migration, and antiviral immunity, but, due to their prevalence in DCM hearts, are also likely to encounter multiple structural proteins of cardiac cells known to be defective in familial DCM. The combined knowledge on DCM-associated gene defects and viruses therefore suggests in-depth studies on genome-environment interactions in DCM pathogenesis which may underlie the high clinical variability observed both in monogenic and virus-associated DCM and have implications for the clinical management of DCM patients.

Clinical features and prognosis of life time non-smokers with severe alpha 1-antitrypsin deficiency

BACKGROUND

The hereditary disorder alpha 1-antitrypsin deficiency is characterised by development of severe emphysema at an early age with smoking being the most significant additional risk factor. The purpose of the present paper was to analyse potential risk factors other than smoking for emphysema and to estimate the prognosis of life time non-smokers.

METHODS

Patients were identified through the files of the Danish alpha 1-antitrypsin deficiency register which contains information on more than 700 persons with the condition. Many of the patients, the non-index cases, were identified from family studies.

RESULTS

There were 75 life time non-smokers with PiZ (27 index cases and 48 non-index cases) aged 20 years or more at entry. Twenty one subjects died during the follow up period. The Standardised Mortality Ratio (SMR) was 3.0 (95% confidence intervals (CI) 1.9 to 4.6). There was no significant difference in SMR between males and females. The SMR was 8.8 (95% CI 5.0 to 14) for the index cases and 0.96 (95% CI 0.3 to 2.3) for the non-index cases based on five deaths. The overall mean % predicted forced expiratory volume in one second (FEV1) at entry was 83% with a significant difference between index cases (54%) and non-index cases (100%) (p < 0.001). The difference in the ratio of FEV1 to forced vital capacity (FVC) was also highly significant with values of 0.57 and 0.79 for index and non-index cases, respectively (p < 0.001). In the non-index group only three had an FEV1% predicted of less than 70%.

CONCLUSIONS

Occupational exposure to airway irritants did not have any significant influence on the development of emphysema. Only a few life time non-smokers develop severe emphysema; most never develop pulmonary symptoms and thus remain undetected unless family members of index cases are screened.

A 30-year perspective on alpha 1-antitrypsin deficiency

The early history of alpha 1-antitrypsin deficiency, in the years between 1962 and 1965, and its impact on the understanding of emphysema abnormalities were reviewed by me in 1989. This report discusses the disease spectrum (including emphysema, liver, and vasculitic diseases) and focuses on the variable clinical expression of the deficiency state. Some new findings that may be relevant to the function of alpha 1-antitrypsin are also considered.

DNA polymorphisms associated with a new alpha 1-antitrypsin PIQ0 variant (PIQ0riedenburg)

A new PIQ0 variant (PIQ0riedenburg) is described; it is caused by a complete deletion of the alpha 1-antitrypsin (alpha 1 AT) gene. The deletion gives rise to four new restriction fragment length polymorphisms (RFLPs) detected with a genomic probe of the 5' region of the gene. Analysis of the RFLPs indicates that the deletion starts immediately upstream of exon Ic. The deletion extends into the 3' flanking region of the gene but does not include the alpha 1 AT-related gene (the PIL gene), which is located 12 kb downstream of the alpha 1 AT gene.