Avaliação da concentração de alfa 1-antitripsina e da presença dos alelos S e Z em uma população de indivíduos sintomáticos respiratórios crônicos / Determination of alpha 1-antitrypsin levels and of the presence of S and Z alleles in a population of patients with chronic respiratory symptoms

OBJETIVO: Determinar a concentração de alfa 1-antitripsina (AAT) e a prevalência dos alelos S e Z em indivíduos sintomáticos respiratórios crônicos. MÉTODOS: Pacientes com tosse crônica e dispnéia foram submetidos à avaliação clínica, espirometria, tomografia computadorizada de tórax, dosagem de AAT por nefelometria e pesquisa das mutações S e Z por reação em cadeia da polimerase. Foram consideradas como variáveis dependentes a concentração de AAT e o tabagismo. RESULTADOS: Dos 89 pacientes incluídos no estudo (44 mulheres; idade média, 51,3 ± 18,2 anos), os alelos S e Z foram detectados em 33,3 por cento e 5,7 por cento, respectivamente, com freqüência gênica dos alelos S e Z de 0,16 e 0,028. Dois pacientes tinham genótipo SZ (AAT < 89 mg/dL). Os pacientes foram divididos em grupos segundo a concentração de AAT: < 89 mg/dL (deficiência, nenhum grupo); 90-140 mg/dL (faixa intermediária, Grupo 1, n = 30); e > 141 mg/dL (normal, Grupo 2, n = 57). A freqüência de fumantes foi igual nos dois grupos, com carga tabágica maior no Grupo 2. O alelo S estava presente em 13 e 14 pacientes dos Grupos 1 e 2, respectivamente, enquanto que o alelo Z estava presente em 2 e 1 paciente dos mesmos grupos. Não houve diferença nos testes de função pulmonar, nem na freqüência de bronquiectasias ou enfisema entre os dois grupos. Os valores espirométricos e as concentrações de AAT foram similares entre fumantes e não-fumantes. Bronquiectasias foram mais freqüentes entre os não fumantes, e enfisema foi mais freqüente entre os fumantes. CONCLUSÕES: Trinta pacientes apresentaram níveis de AAT abaixo da média esperada para os genótipos MM e MS, e este fato não pode ser explicado por uma freqüência maior dos alelos S e Z.

OBJECTIVE: To determine the levels of alpha-1 antitrypsin (AAT) and the presence of S and Z alleles in patients with chronic respiratory symptoms. METHODS: Patients with chronic cough and dyspnea were submitted to clinical evaluation, pulmonary function tests, high-resolution computed tomography, nephelometric determination of AAT and determination of S and Z alleles by polymerase chain reaction. Smoking and AAT levels were considered the dependent variables. RESULTS: Of the 89 patients included in the study, 44 were female. The mean age was 51.3 ± 18.2 years. The S and Z alleles were detected in 33.3 percent and 5.7 percent, respectively, and the gene frequency was 0.16 and 0.028, respectively. Two patients were SZ heterozygotes (AAT levels < 89 mg/dL). The patients were divided into groups based on AAT level: < 89 mg/dL (deficiency, no group); 90-140 mg/dL (intermediate, Group 1, n = 30); and > 141 mg/dL (normal, Group 2, n = 57). The frequency of smokers was the same in both groups, although tobacco intake was greater in Group 2. The S allele was present in 13 and 14 patients in Groups 1 and 2, respectively, whereas the Z allele was present in 2 and 1 patient in the same groups. There was no difference in the results of pulmonary function tests or in the frequency of bronchiectasis or emphysema between the two groups. Spirometric values and AAT levels were similar in smokers and nonsmokers. Bronchiectasis was more common in nonsmokers, and emphysema was more common in smokers. CONCLUSIONS: Thirty patients presented AAT levels lower than the mean values found in patients with the MM or MS genotype, and this fact could not be explained by an increased frequency of S and Z alleles.

Diagnosis of alpha-1-antitrypsin deficiency by DNA analysis of children with liver disease

BACKGROUND: Alpha-1-antitrypsin deficiency is a genetic disorder which is transmitted in a co-dominant, autosomal form. Alpha-1-antitrypsin deficiency affects mainly the lungs and the liver leading, in the latter case, to neonatal cholestasis, chronic hepatitis or cirrhosis. A precise diagnosis of Alpha-1-antitrypsin deficiency may be obtained by biochemical or molecular analysis. OBJECTIVE: The purpose of this study was to use DNA analysis to examine the presence of an alpha-1-antitrypsin deficiency in 12 children suspected of having this deficiency and who showed laboratory and clinical characteristics of the disease. PATIENTS AND METHODS: Twelve patients, aged 3 months to 19 years, who had serum alpha-1-antitrypsin levels lower than normal and/or had hepatic disease of undefined etiology were studied. The mutant alleles S and Z of the alpha-1-antitrypsin gene were investigated in the 12 children. Alpha-1-antitrypsin gene organization was analyzed by amplification of genoma through the polymerase chain reaction and digestion with the restriction enzymes Xmnl (S allele) and Taq-1 (Z allele). RESULTS: Seven of the 12 patients had chronic liver disease of undefined etiology and the other five patients had low serum levels of alpha-1-antitrypsin as well as a diagnosis of neonatal cholestasis and/or chronic liver disease of undefined etiology. Five of the 12 patients were homozygous for the Z allele (ZZ) and two had the S allele with another allele (*S) different from Z. CONCLUSION: These results show that alpha-1-antitrypsin deficiency is relatively frequent in children with chronic hepatic disease of undefined etiology and/or low alpha-1-antitrypsin levels (41.6 per cent). A correct diagnosis is important for effective clinical follow-up and for genetic counseling.

Molecular diagnosis of Huntington disease in Brazilian patients

Huntington disease (HD) is a progressive neurodegenerative disorder with autosomal dominant inheritance, characterized by choreiform movements and cognitive impairment. Onset of symptoms is around 40 years of age and progression to death occurs in approximately 10 to 15 years from the time of disease onset. HD is associated with an unstable CAG repeat expansion at the 5' and of the IT15 gene. We have genotyped the CAG repeat in the IT15 gene in 44 Brazilian individuals (42 patients and 2 unaffected family members) belonging to 34 unrelated families thought to segregate HD. We found one expanded CAG allele in 32 individuals (76 per cent) belonging to 25 unrelated families. In these HD patients, expanded alleles varied from 43 to 73 CAG units and normal alleles varied from 18 to 26 CAGs. A significant negative correlation between age at onset of symptoms and size of the expanded CAG allele was found (r=0.6; p=0.0001); however, the size of the expanded CAG repeat could explain only about 40 per cent of the variability in age at onset (r2=0.4). In addition, we genotyped 25 unrelated control individuals (total of 50 alleles) and found normal CAG repeats varying from 16 to 33 units. The percentage of heterozigocity of the normal allele in the control population was 88 per cent. In conclusion, our results showed that not all patients with the "HD" phenotype carried the expansion at the IT15 gene. Furthermore, molecular diagnosis was possible in all individuals, since no alleles of intermediate size were found. Therefore, molecular confirmation of the clinical diagnosis in HD should be sought in all suspected patients, making it possible for adequate genetic counseling.