The level of 6-phosphogluconate dehydrogenase (6-PGD) activity in a patient with 1p terminal deletion suggests that the gene locus is not distal to sub-band p36.3 on chromosome 1.

A rare case of chromosome 1p deletion is reported in a mentally retarded male infant with a derived chromosome: 45,XY,-1,-13,tdic(1;13)(1qter----1p36.2::13p11.2----++ +13qter). Parental chromosomes were normal. Since the patient's 6-PGD specific activity was in the normal range, it is probable that he retained both 6-PGD alleles. Consequently, if a dosage affect exists, then the locus for 6-PGD must be proximal to 1p36.3.