ATP7B and Wilson disease: However, the remaining 2% of WD patients, with a classic hepatic or neurologic phenotype and abnormal copper balance, show only a single deleterious mutation (heterozygous) or no mutation after standard sequencing analysis of ATP7B. Therefore, in these problematic WD cases, we hypothesized that deleterious mutations reside in intronic regions of ATP7B. Here, we tested this hypothesis by sequencing the entire ATP7B gene, including introns, from 10 such WD families.