Despite lifelong restriction of dietary galactose, individuals with classic galactosemia suffer from various long-term complications, including speech, cognitive and movement problems. The underlying mechanisms are unknown, and treatments are limited. To shed light on this issue, Ryan et al. investigated long-term disease outcomes using a GALT-null Drosophila model of galactosemia that they developed previously. They report that, similar to patients, mutant flies develop a long-term movement defect that worsens rapidly with age. As little as 2.5% residual expression of the missing enzyme, GALT, is sufficient to improve long-term outcomes, whereas low-level exposure to galactose during development had no effect. These findings challenge current theories about long-term complications of galactosemia and confirm that this fly model will be useful for further studies of the disease. Page 796

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