Aase-Smith syndrome II: A genetic disorder that may be detected during early infancy and is characterized by the presence of three bones (phalanges) within the thumbs (triphalangeal thumbs) rather than the normal two and abnormally reduced production of red blood cells (hypoplastic anemia).

The exact cause of the syndrome is unknown. However, most evidence suggests that the disorder is inherited as an autosomal recessive trait.

The syndrome is named for the American dysmorphologists (birth-defect experts) Jon Aase and David W. Smith. Alternative names for the syndrome include: Anemia and triphalangeal thumbs Congenital anemia and triphalangeal thumbs Hypoplastic anemia-triphalangeal thumbs, Aase-Smith type.