Moreover, in contrast to some other repair defective syndromes, SS is a heterogeneous disease with five independent loci identified: SCKL1, which bears a mutation that creates an alternative splicing site in the ATR gene [2]; SCKL2, previously mapped by us in the chromosomal region 18p11.31-q11.2 [3]; SCKL3, mapped in the region 14q23-q24 [4]; SCKL4 that has a mutation in the CENPJ gene [5]; and the recently reported SCKL5 that harbors mutations in CEP152[6]. This evidence concerns the gene ATR and synovial sarcoma.