Three patients were found to have large deletions: one APC promoter deletion in a patient with an extensive family history of cancer, a multiple-exon deletion in BRCA1 in a patient with personal and family history of HBOC-associated cancers, and a large multiple exon deletion in PMS2 in a patient with a family history of both LS- and HBOC-associated cancer. Here, BRCA1 is linked to Leigh syndrome.