Hanhart syndrome is an extremely rare congenital anomaly, grouped under the 'oromandibular limb hypogenesis syndromes', a group of rare conditions involving malformations of the tongue, mandible, and limbs. Hanhart syndrome is characterized by hypoglossia, hypodactylia, peromelia, and micrognathia. The syndrome shows a marked degree of variability, with affected children showing either some or all of the symptoms.
To date, only about 30 cases of Hanhart syndrome have been reported in literature. It is presumed that the syndrome is a manifestation of hemorrhagic lesions developing during embryonic development. The disorder is not preventable, and treatment may involve orthopedic and/or plastic surgery to correct the anomalies.