Decreased circulating apolipoprotein A-I concentration 2018-02-25T15:04:10Z Decreased apo-AI level Concentration of apolipoprotein A-I below the lower limit of normal. Apolipoprotein A-I is the major protein component of high density lipoprotein (HDL) in plasma. Defects in this gene are associated with HDL deficiencies, including Tangier disease. Decreased apolipoprotein AI level Decreased apoA-I level Decreased circulating apolipoprotein concentration