Interstitial deletion of the distal long arm of chromosome 4.

We report the first case of an interstitial deletion of the distal long arm of chromosome 4 (q31.22----q34.2). The major clinical features are described and compared to those of other published reports of del 4q, mainly those sharing a common deleted segment with the present case (both interstitial and terminal). This comparison suggests that the characteristic phenotype attributed to terminal deletions of 4q31----qter probably mainly results from loss of the segment q31----q33-34.