GALC and Krabbe disease: Based on the incidence of Krabbe disease in the United States (1 in 100,000 births) [29], [30], the estimated combined frequency of all functionally-relevant GALC mutations is 0.003, implying a population frequency of the 30-kb deletion of approximately 0.0013, very similar to the frequency of 0.0011 we have detected in the present study (5 deletions in 4660 chromosomes of 2330 controls).