TY - JOUR T1 - What is Pi (proteinase inhibitor) null or PiQO?: a problem highlighted by the alpha 1 antitrypsin Mheerlen mutation. JF - Journal of Medical Genetics JO - J Med Genet SP - 27 LP - 29 DO - 10.1136/jmg.29.1.27 VL - 29 IS - 1 AU - N Kalsheker AU - K Hayes AU - S Weidinger AU - A Graham Y1 - 1992/01/01 UR - http://jmg.bmj.com/content/29/1/27.abstract N2 - alpha 1 antitrypsin deficiency is associated with predisposition to the development of pulmonary emphysema and childhood cirrhosis. There are two common deficiency alleles in the European population, proteinase inhibitor (Pi) Z and S. In addition, there are rare Pinull or QO variants which can be difficult to diagnose. A family assigned as having the PiQO allele by AAT protein quantification and isoelectric focusing was shown by DNA sequencing to have the PiMheerlen mutation (Pro369-Leu). This highlights the difficulties of diagnosis of PiQO. ER -