Editor—Uniparental disomy (UPD) is the inheritance of both copies of a chromosome or a chromosomal region from one parent.1 2 When both chromosomes from one parent are present the phenomenon is called “heterodisomy”, whereas the presence of two copies of only one of the parental chromosomes is called “isodisomy”. A map of UPD for the human genome has been proposed and covers several areas of the 22 autosomes and the X chromosome.1 3 Not unexpectedly, growth abnormalities and other endocrine disturbances appear to be frequent in patients with UPD for whole chromosomes or even for small chromosomal regions.3 Although UPD appears to be rare among patients with various congenital defects,4 disomic human sperm nuclei are present relatively frequently and without interchromosomal differences.5 The true incidence of UPD may be significantly higher if the various molecular and cytogenetic possibilities for disomy are considered, and the genome is tested by densely located polymorphic markers.1-5

UPD for chromosome 2 has been reported in five patients,2three cases of heterodisomy and two of isodisomy.6-10 No particular clinical phenotype was seen in one of the patients,7 but intrauterine growth retardation (IUGR), oligohydramnios, and pulmonary and genital hypoplasia were present in all of the other cases.6 8-10 Additional manifestations in the individual patients were probably the result of the cytogenetic event that preceded UPD; two of the patients had confined placental mosaicism for trisomy 29 10 and another had trisomy 2 mosaicism in amniotic fluid culture.6

In the context of genetic studies for the mapping of Carney complex (CNC), a normal subject was found to have only maternal alleles of two polymorphic markers mapping to the short arm of chromosome 2. The absence of a microdeletion or other chromosomal anomalies (by classic …