Correspondence

doi: 10.1002/mgg3.188 Background Bloom syndrome is an autosomal recessive disorder characterized by extraordi-nary cancer incidence early in life and an average life expectancy of ~27 years. Premature stop codons in BLM, which encodes a DNA helicase that functions in DNA double-strand-break repair, make up the vast majority of Bloom syndrome mutations, with only 13 single amino acid changes identified in the syndrome. Sequencing projects have identified nearly one hundred single nucleotide variants in BLM that cause amino acid changes of uncertain significance. Methods and Results Here, in addition to identifying five BLM variants incapable of complementing certain defects of Bloom syndrome cells, making them candidates for new Bloom syndrome causing mutations, we characterize a new class of BLM vari-ants that cause some, but not all, cellular defects of Bloom syndrome. We fin