Hereditary deficiency of erythrocyte acetylcholinesterase

A 36-year-old white man was found to have low erythrocyte acetylcholinesterase activity. Plasma cholinesterase activity was normal. The propositus had mild anemia and moderate elliptocytosis, but was asymptomatic. A sister, brother, father, and nephew were hematologically normal, but had slightly subnormal red cell acetylcholinesterase activities. There was no exposure to organophosphates, and paroxysmal nocturnal hemoglobinuria was excluded. Mixing experiments failed to demonstrate the absence of an activator or the presence of an inhibitor. The propositus enzyme showed normal kinetics for the substrate and various inhibitors, normal thermostability, and electophoretic migration. Major protein bands of the red cell membrane were normal by electrophoresis. Membrane cholesterol and phospholipid content were also normal. The mild anemia is presumably secondary to the presence of moderate elliptocytosis. The pattern of inheritance of the variant gene is unclear, but the propositus may be homozygous for the abnormal allele, and other family members may be heterozygous.