Editor—There are many reports of partial trisomy 8p in the offspring of balanced translocation carriers.1-3 However, in these cases the effect of the partial trisomy is usually masked by the phenotypic consequences of partial monosomy of the partner chromosome.

Partial trisomy for 8p also results from the well known inverted duplication of 8p usually described as inv dup(8)(p11.2p23); this rearrangement, however, also results in partial monosomy for the segment 8p23.1→8pter.4-6 The inv dup(8) is associated with a well defined clinical syndrome,5-9 the childhood phenotype of which includes neonatal feeding problems, hypotonia, structural brain abnormalities, facial dysmorphology, malformed, low set ears, and severe developmental delay. In older patients the facial traits are less characteristic, mental retardation is profound, and spastic paraplegia and orthopaedic problems are frequent. It is known that patients with deletion of 8p23→pter as their sole chromosome abnormality have a near normal phenotype with only mild mental retardation and minimal dysmorphology.10-12 The phenotypic findings of inv dup(8)(p11.2p23) are therefore considered to arise primarily as a result of the duplicated segment 8p21.

More recent reports have described smaller, more distal duplications of 8p in which there is no evidence of any monosomic segment.13-17 Dhooge et al 13 described the transmission of a duplication dup(8)(p22→p23.1) or (p21.3→p22) from a mother to her two children. The associated clinical features were mild mental retardation, short stature, and hypertelorism. Engelen et al 14 described a similar case of transmission of partial trisomy 8p resulting from dup(8)(p22→p23.1) from a mother to her two sons. In this family, mental retardation was mild and there was no growth retardation, only the mother showed slight facial dysmorphology. Barber et al 15recently described seven families with small duplications of 8p23.1 and reviewed five families previously reported in abstract form.16 17 …