Our study of the mutation spectrum of other genes among Russian patients showed that gross deletions/duplications in the STRC and USH2A genes and the four most frequent mutations (c.11864G>A in the USH2A gene, c.2171_2174delTTTG in the STRC gene and c.107A>C and c.1001G>T in the SLC26A4 gene) accounted for 38% of diagnoses framed with the developed MPS panel. The gene discussed is SLC26A4; the disease is mucopolysaccharidosis.