Macrognathia refers to an abnormally large jaw, which can be caused by conditions like pituitary gigantism, Paget's disease of bone, or acromegaly in adults. Clinical features of macrognathia include mandibular protrusion, an enlarged mandible, a gummy smile showing excessive gums, a prominent chin button, and a less steep angle between the ramus and body of the mandible. Treatment may involve osteotomy to decrease the length of the mandible followed by orthodontic treatment.