Idiopathic multicentric osteolysis is a very rare syndrome characterized by progressive loss of bone, usually the capsal and tarsal bones, resulting in deformity and disability, as well as chronic renal failure in many cases. The bone and renal disorders are sometimes associated with intellectual deficit and facial abnormalities.

A morphological abnormality of the mouth in which the angle of the mouth is downturned. The oral commissures are positioned inferior to the midline labial fissure.