Further examples confirming the existence of Pi null (Pi-).

The existence of the Pi- allele (Pi null) was envisaged by Talamo when he discovered a subject whose serum contained no alpha-1-antitrypsin. We were able to demonstrate that a single dose of this allele exists in three families which we studied. In a fourth family, the propositus carried this allele in duplicate (phenotype Pi- -), which agrees with the results of the quantitative analyses carried out on the parents. The importance of the Pi- allele is envisaged and the necessity of the genetic survey is generally essential to demonstrate its existence.