Familial balanced insertion (5;10) and monosomy and trisomy (10) (q24.2----q25.3).

The phenotype of a boy with monosomy of a small segment of chromosome (10) (q24.2----q25.3) is described. In his family a balanced insertion (5;10) is found in three generations. Moreover there are two persons who are trisomic for the same small segment of chromosome 10 for which the boy is monosomic.