There are several reports of congenital absence of bilateral mandibular central incisors: *Lehman (1976) reported a pair of siblings with congenital bilateral missing mandibular central incisors. There was no other information about associated abnormalities and the status of their parents was unknown 1 . * Kurtz and Brownstein (1974) described the absence of the mandibular central incisors in a man and 2 of his 3 children, a son and daughter. Dyslexia appeared to be segregating independently in this family 2 . *Pitts (1923) described a family in which the mandibular central incisors were missing in 4 male sons. Again, the status of the parents is unknown 3 .
Only two reports of a solitary mandibular central incisor were identified: *Oberoi and Vargervik (2005) described a series of three siblings and their mother with velocardiofacial syndrome. One sibling had a solitary central maxillary incisor, while another sibling had a solitary central mandibular incisor. The third sibling and mother had normal dentition 4 . *Miller ( ) reported a solitary central mandibular incisor seen in three generations in a Japanese family 5 .
CASE REPORT
An 11 year-old twin boy presented to the office of the senior author, MMA, for evaluation of a neck mass. The mass was first noticed one month prior to presentation. There were no associated symptoms such as pain, changes in phonation, difficulty breathing, or swallowing. He was otherwise healthy with no other medical problems or developmental abnormalities, and no recent illnesses. There were no known genetic anomalies in the family, and his fraternal twin brother was healthy with no medical problems.