Protease inhibitor phenotype BsaskatoonM is not associated with emphysema - a 20-year follow-up study

To investigate the association between the PiBsaskatoon variant of alpha-1 protease inhibitor (a1 Pi), present in the heterozygous state, and the development of emphysema.

Twenty-year follow-up in the third generation of a family with the variant, naturally controlled with regard to both environmental influences and other genetic factors.

University teaching hospital.

Ten siblings, five with PiBsaskatoonM phenotype and five with PiM phenotype, 33 to 46 years of age.

Respiratory symptoms and smoking histories; pulmonary function tests, including static lung volumes, dynamic lung volumes before and after salbutamol 200 mg, and diffusing capacity; allergen prick skin tests; serum a1 Pi level, chest radiographs and high resolution computerized tomography lung scans

The two groups of siblings had similar mean ages, smoking histories and prevalence of current mild respiratory symptoms. Pulmonary function data showed normal mean values and no statistically significant differences for all the variables between the two groups. Chest radiographs were normal in all subjects. High resolution computerized tomography scans were normal in eight subjects, and demonstrated mild and very mild centrilobular emphysema in the two subjects with greatest smoking histories (approximately 30 pack-year each); both of these were PiBsaskatoonM phenotype.

There is no evidence of an association between a1 Pi phenotype PiBsaskatoonM and the development of emphysema.