Mondo Description Hanhart syndrome is a rare condition that primarily affects the craniofacial region and the limbs (arms and legs). People affected by this condition are often born with a short, incompletely developed tongue; absent or partially missing fingers and/or toes; abnormalities of the arms and/or legs; and an extremely small jaw. The severity of these physical abnormalities varies greatly among affected people, and children with this condition often have some, but not all, of the symptoms. The cause of Hanhart syndrome is not fully understood. Treatment depends on the signs and symptoms present in each person.