A STUDY ON THE FREQUENCY OF THE DIFFERENT ALPHA-1-ANTITRYPSIN PHENOTYPES IN A POPULATION FROM BARCELONA, SPAIN

BACKGROUND: Severe alpha-1-antitrypsin (AAT) deficiency is caused by h omozygous inheritance of gene Z, and is associated with a high risk of developing pulmonary emphysema. Determination of frequencies of diffe rent genes associated with the deficiency (especially S and Z) gives a clue to estimate the number of individuals homozygous PiZZ, carrying a high risk for pulmonary disease, in any given population. PATIENTS A ND METHODS: Pi phenotypes of 440 healthy individuals were determined b y means of isoelectrofocusing in polyacrylamide gel. Seric values of A AT were determined by immunonephelometry. Mean age of participants was 30 years (range 18-49 yrs.). Results are compared with other publishe d series. RESULTS: Distribution of phenotypes was: PiMM 333 individual s (75%), PIMS 84 (19%), PiMZ 14 (3%), PiSS 4 (0.9%), PiM 3 (0.6%), PiM F 1 (0.2%), PiMP 1 (0.2%). The corresponding gene frequencies were Pi M 87%, PiS 10.4%, and Pi*Z 1.5%. Normal values of AAT (phenotype PIMM ) established in our laboratory were 116-232 mg/dl (21-41 micromol/l) (mean +/- 2 SD). According to Hardy-Weinberger ecuation, expected freq uency of PiZZ individuals in our area would be 225 per milion. CONCLUS IONS: The frequency of Z gen individuals observed in our study is one of the highest in the Iberian Peninsula, but lower than the frequency in nothern Europe. According to these results, AAT deficiency (PiZZ) i s not a rare condition in contrast with the small number of patients d iagnosed. The gen frequency of the S variant is higher than that of th e rest of Europe, and similar to others found in some Spanish populati ons.