...there were 3 sets of identical twins in which one twin had no [olfactory bulb] and the other twin had a normal OB. In all three cases, the person without an OB could actually smell better than their twin. Overall, in that database, they found that 0.6% of women and 4.25% of left-handed women had the same condition.
Read more in People missing the scent region of their brain can still smell at Massive Science.