Alpha 1-antitrypsin deficiency (α1-antitrypsin deficiency, A1AD) is a genetic disorder that causes defective production of alpha 1-antitrypsin (A1AT), leading to decreased A1AT activity in the blood and lungs, and deposition of excessive abnormal A1AT protein in liver cells. There are several forms and degrees of deficiency; the form and degree depend on whether the sufferer has one or two copies of a defective allele. In the literature it has been described as either a recessive or co-dominant trait as there is some evidence that smoking heterozygotes are affected. Severe A1AT deficiency causes panacinar emphysema or COPD in adult life in many people with the condition (especially if they are exposed to cigarette smoke). The disorder can lead to various liver diseases in a minority of chi