An analysis of common isodisomic regions in five mUPD 16 probands

Intrauterine growth retardation (IUGR) with or without additional abnormali ties is recognised as a common feature of maternal uniparental disomy for c hromosome 16 (mUPD 16) and is usually associated with confined placental mo saicism (CPM). Although it is likely that the CPM largely contributes to th e IUGR, postnatal growth retardation and other common abnormalities may als o be attributed to the mUPD. Five cases with mUPD 16 and CPM were analysed for common regions of isodisomy using polymorphic markers distributed along the length of the chromosome. In each case the aberration was consistent w ith a maternal meiosis I error. Complete isodisomy was not detected in any of the patients although two patients were found to be mixed with both iso- and heterodisomy. Interestingly, the patient with the greater region of is odisomy was the most severely affected. The fact that there were no common regions of isodisomy in any of the patients supports the hypothesis that im printed genes, rather than recessive mutations, may play a role in the shar ed phenotypes.