RT-PCR analysis of mRNA samples from five unrelated patients with mutations affecting the 3′ end of exon 3 (c.550G>C, c.550G>A, and c. 550+5 G>A) performed by our group, showed an additional transcript lacking exon 3. Second, the semi-quantitative comparison of the expression of both variants in controls and patients on agarose gels, revealed an apparently higher expression of the exon 3 skipped variant in these patients than in controls