Relationship between a Mild α1 Proteinase Inhibitor Deficiency and Respiratory Symptoms in a Family

Abstract

A 34-year-old man with pulmonary emphysema was found to have a mild α1 proteinase inhibitor (α1 PI) deficiency. α1 PI status was investigated in this patient and in 35 members of his family. The α1 PI investigations included α1 PI concentration and phenotype and serum inhibitory capacity for trypsin and pancreatic elastase. Fifteen members of the family had α1 PI concentration and inhibitory capacities below the lower normal limit. Five of these members were characterized by the heterozygous MP phenotype and the 10 others by an apparently homozygous M phenotype, in which the M allele may be associated with another unidentified deficiency allele. Two members of the family had α1 PI concentration and elastase inhibitory capacity below the lower normal limits and trypsin inhibitory capacity within the normal range. They were both characterized by the MP phenotype. Six of these 17 members (three of PI type M and three of PI type MP) showed chronic pulmonary symptoms, whereas among the 19 α1 PI non deficient members, no member had a history of significant pulmonary symptoms.