Purpose: The phenotype correlations for interstitial duplications that include the Prader-Willi/Angelman syndrome critical region are not well established. We describe two such duplication cases, one of which was of maternal origin and the other was paternal.
Methods: High resolution G-banding, fluorescence in situ hybridization (FISH) for SNRP-N and D15S10 were used for cytogenetic analysis. Southern blot analyses based on parent of origin specific DNA methylation at D15S63 (PW71) locus were utilized for detection of methylated and unmethylated fragments.
Results: The duplication was established by the FISH analysis. The molecular pattern suggested a maternal origin of the duplication in patient 1 and a paternal origin in patient 2. Patient 1 (2 years old) had developmental and speech delays with pervasive developmental disorder or mild autism, strabismus, and normal growth parameters with seizures. Patient 2 (16 years old) had global developmental delay, verbal IQ of 94, depression, obesity, food-seeking behavior, and significant behavioral problems that included self-injurious tendencies. Neither patient had significant dysmorphic features or abnormalities of internal organs.
Conclusion: The two cases suggest that some patients with 15q11.2q12 duplication may have significant anomalies, and there appear to be phenotypic differences between maternal and paternal transmission of the duplication.