Alpha-1-proteinase inhibitor and pulmonary haemorrhage in systemic vasculitis.

Alpha-1-proteinase inhibitor phenotypes and levels were examined in 40 antineutrophil cytoplasmic antibody positive cases of systemic vasculitis. An excess of PiZ and PiS alleles were associated with the development of pulmonary haemorrhage and alpha-1-proteinase inhibitor levels were lower in the subgroup with pulmonary haemorrhage. However, this allelic imbalance and reduced alpha-1-proteinase inhibitor level was not confined to antiproteinase 3 positive patients and did not appear to be associated with other organ involvement or disease severity.