Martinelli et al. (1987) described a father and 2 sons with idiopathic bilateral hypertrophy of the masseter muscles beginning in the teens. No evidence of bruxism (grinding of teeth) or unusual chewing habits was discovered. Martinelli et al. ... Martinelli et al. (1987) described a father and 2 sons with idiopathic bilateral hypertrophy of the masseter muscles beginning in the teens. No evidence of bruxism (grinding of teeth) or unusual chewing habits was discovered. Martinelli et al. (1987) found records of other cases of 'strong lower faces' in several members of families with a family history of 'large, square jaws.' CT examination, performed in 2 cases, showed homogeneous bilateral enlargement of the masseter muscles consistent with true hypertrophy. One of the sons had mild thoracolumbar scoliosis.