Hi, I'm working on a variant analysis to detect disease-causing variants in Mucopolysaccharidosis IVA patients. I'm using Sanger sequencing method which includes exonic regions and a minimum of 100 bp intronic sequences from both ends of exons. However, I couldn't find pathogenic variants in several patients. Is it possible if that patients do not have pathogenic variants in exon/splice site despite showing disease characteristics? Thank you