Received: 18 January 2017 | Revised: 7 June 2017 | Accepted: 2 August 2017 DOI: 10.1002/ajmg.a.38459 ORIGINAL ARTICLE Genotypic-phenotypic features and enzyme replacement therapy outcome in patients with mucopolysaccharidosis VI from Turkey Mustafa Kılıç 1 | Ali Dursun 2 | Turgay Coşkun 2 | Ayşegül Tokatlı 2 | Rıza K. Özgül 2 | Didem Yücel-Yılmaz 2 | Mehmet Karaca 3 | Deniz Doğru 4 | Dursun Alehan 5 | Sibel Kadayıfçılar 6 | Aydan Genç 7 | Handan Turan-Dizdar 7 | Burhanettin Gönüldaş 8 | Sema Savcı 9 | Melda Sağlam 9 | Cemalettin Aksoy 10 | Umut Arslan 11 | Hatice-Serap Sivri 2 1 Sami Ulus Children Hospital, Division of Metabolism, Ankara, Turkey 2 Hacettepe University Children Hospital, Division of Metabolism, Ankara, Turkey 3 Faculty of Science and Arts, Department of Biology, Aksaray University, Aksaray, Turkey 4 Hacettepe University Children Hospital, Division of Pediatric Pulmonology, Ankara, Turkey 5 Hacettepe University Children Hospital, Division of Pediatric Cardiology, Ankara, Turkey 6 Faculty of Medicine, Department of Ophthalmology, Hacettepe University, Ankara, Turkey 7 Faculty of Medicine, Department of Ear Nose Throat, Division of Audiology, Hacettepe University, Ankara, Turkey 8 Faculty of Medicine, Department of Ear Nose Throat, Hacettepe University, Ankara, Turkey 9 Faculty of Health Sciences, Department of Physiotheraphy and Rehabilitation, Hacettepe University, Ankara, Turkey 10 Faculty of Medicine, Department of Orthopaedics and Traumatology, Hacettepe University, Ankara, Turkey 11 Faculty of Medicine, Department of Biostatistics, Hacettepe University, Ankara, Turkey Correspondence Mustafa Kılıç, Sami Ulus Children Hospital, Division of Metabolism, Ankara, Turkey, Babur cad. No: 44, 06080 Altındağ/Ankara. Email: kilickorkmaz@yahoo.com.tr Mucopolysaccharidosis type VI (MPS VI) is a lysosomal storage disorder (LSD) characterized by a chronic, progressive course with multiorgan involvement. In our study, clinical, biochemical, molecular findings, and response to enzyme replacement therapy (ERT) for at least 6 months were evaluated in 20 patients with MPS VI. Treatment effects on clinical findings such as liver and spleen sizes, cardiac and respiratory parameters, visual and auditory changes, joints’ range of motions, endurance tests and changes in urinary glycosaminoglycan excretions, before and after ERT were analyzed. ERT caused increased physical endurance and decreased urinary dermatan sulfate/chondroitin sulfate ratios. Changes in growth parameters, cardiac, respiratory, visual, auditory findings, and joint mobility were not significant. All patients and parents reported out an increased quality of life, which were not correlated with clinical results. The most prevalent mutation was p.L321P, accounting for 58.8% of the mutant alleles and two novel mutations (p.G79E and p.E390 K) were found. ERT was a safe but expensive treatment for MPS VI, with mild Ethics approval: This study was conducted as a single-center, open-label study. The study protocol was approved by the Medical Ethics Committee of Hacettepe University. Am J Med Genet. 2017;1–14. wileyonlinelibrary.com/journal/ajmga © 2017 Wiley Periodicals, Inc. | 1