Familial Angelman syndrome with a crossover in the critical deletion region

More than two thirds of the patients with Angelman syndrome (AS) carry a deletion or other chromosomal abnormality in the 15q11-13 region. A much less frequent cause (4%) is paternal uniparental disomy of the entire chromosome. In general no abnormalities are detectable in familial cases and an inherited submicroscopic deletion was described only once. Here a familial case of 2 sibs with AS is reported. No major cytogenetic or molecular abnormality was identified, but a recombination event had occurred in the AS critical region. The AS locus, D15S113, D15S10, D15S11, and D15S18 mapped proximal and the GABRB3 gene, D15S97, the GABRA5 gene, and D15S12 distal to the crossover site. This recombination within the AS critical region confirmed the exclusion of GABRB3 as a candidate gene for AS. Other markers and candidate genes can be tested genetically as well for a possible role in AS.