Van der Kraan et al. (1994) reported that deletion of exon 18 of the GAA gene is a frequent mutation in Pompe disease (GSD2; 232300). Huie et al. (1994) found this mutation in patients with both infantile and adult forms of this disease. Vorgerd et al. (1998) found homozygosity for the exon 18 deletion in 2 affected sibs and an unrelated patient with adult-type GSD II.
Boerkoel et al. (1995) found a deletion of exon 18 of the GAA gene in 3 unrelated compound heterozygous patients, 2 of whom were infants, and 1 an adult. The second mutation in each of these patients was different. The infants with Pompe disease were French Canadian and Dutch. The adult was a woman of German extraction who had first consulted her physician at age 39 years for progressive proximal muscle weakness and respiratory insufficiency. In retrospect, she could recall limitation in her activity as far back as early adulthood. In one of the infants, there was deletion of lys903 (606800.0007); in the other, there was a leu299-to-arg substitution (606800.0008). In the adult, the authors observed a T-to-G transversion at position -13 of intron 1 (606800.0006).
Although Kroos et al. (1995) found deletion of exon 18 in the infantile and adult forms of the disease, those homozygous for this mutation and heterozygous for this mutation in combination with deletion of 525T (606800.0014) had the infantile form of Pompe disease; however, patients with deletion of exon 18 or deletion of 525T in combination with transversion of T to G at position -13 (606800.0006) had the juvenile or the adult form, suggesting that the intronic mutation was a mild mutation.
