Possible supernumerary chromosome associated with hypodontia.

Thosen (Amer. J. phys. Anthrop., [n.s. 10:155, 1952) listed dominant, irregular donsinant, recessive, and sex-linked genes as the explanation for hypodontia. Grahnhn (Odont. Revy, 7, Sup)pl. 3, 1956) concluded from studies of Swedish families that dominant genes were involved in the majority of cases of hypodontia and that probably a number of genetic entities were associated with its occurrence. Evidence exists for genetic origin in the etiology of hypodontia; however, the mode of transmission is still unsolved. During a survey for chromosome anomalies in oral congenital diseases, a definite abnormality was observed in the karyotype of cells analyzed in an 11-year-old boy with hypodontia. On oral examination, he demonstrated multiple caries in primary and permanent teeth, anterior crowding, and gingivitis. The mandibular right second bicuspid was missing clinically and radiographically. Physical examination revealed a heart murmur and deafness in one ear. His medical history disclosed scarlet fever at age 3 and a tonsillectomy at 8 years of age. His four sisters and one brother were health and had no record of missing teeth. Chromosome preparations, using the method of P. S. Moorhead and others