PAX6 and Anosmia: In addition to the Small eye ocular anomalies,5 the olfactory bulbs of heterozygote mice are reduced in size.6 Heterozygous PAX6 mutation in humans is known to cause aniridia7 and hyposmia or anosmia.8 Such parallels between human and rodent developmental anomalies suggest that aniridia presents a unique opportunity to study the multiple roles of PAX6 in humans.