Editor—X;autosome translocations are very rare and occur at an estimated frequency of 1:300 000.1According to the hypothesis of Lyon,2 there is a random and irreversible inactivation of one of the two X chromosomes in the female, occurring at an early stage of development. In patients with an X;autosome translocation, X inactivation occurs at random but is followed by cellular selection, favouring the better genetic balance.3 Accordingly, nearly 95% of patients with balanced X;autosome translocations show a skewed inactivation of the normal X chromosome in almost all cells, thereby avoiding somatic monosomy or X chromosome disomy, while patients with unbalanced X;autosome translocations have the der(X) constantly inactivated in 91% of the cases in order to obtain the most optimal balance of the genome.1 We report here a woman who was referred for chromosome analysis because of four consecutive first trimester spontaneous miscarriages following the birth of a healthy daughter.

The patient is short (152 cm), but otherwise healthy, with no dysmorphic features or malformations. Chromosome analysis of peripheral blood showed an apparently pure Xp deletion using conventional banding techniques. Chromosome microdissection of the aberrant Xp was performed according to Senger et al,4using an inverted phase contrast microscope (Axiovert 135) and a micromanipulator (Narishige MMO-2YD). Six fragments containing the whole aberrant Xp were excised and transferred to a 10 nl collection drop containing 10 mmol/l TRIS-HCl, pH 7.5, 10 mmol/l NaCl, 0.1% SDS, and 0.5 mg/ml proteinase K. After digestion with proteinase K, the collection drop was transferred to a 250 μl reaction tube containing 5 μl of PCR mixture: 5 μmol/l 6-MW-primer - …