Dynamic Gait Analysis in Children With Mucopolysaccharidosis Type IVa

Mucopolysaccharidosis Type IVa (MPS IVa, Morquio Disease) is a rare inherited lysosomal storage disorder caused by deficiency of the enzyme galactose-6-sulfatase.

Children with this disease accumulate a chemical called keratan sulphate, which stops their skeletons developing properly. They are very short in stature and many of their joints are unstable. Children with MPS IVa walk in a different way to other people due to a combination of lax ligaments and skeletal problems such as knock-knees.

Human walking involves the coordinated movements of all four limbs. As we walk, the arms swing oppositely to the legs. This movement pattern is very different in children with MPS IVa. This change seems to involve the whole musculoskeletal system and depends on the severity of the disease.

Recent studies in children with MPS IVa describing walking pattern have concentrated solely on the lower or upper limb respectively, and have not looked at the interaction of the upper and lower limbs during walking.

To our knowledge, the mechanics of walking in children with MPS IVa has not been investigated using a dynamic gait analysis tool (using cameras, sensors and electrodes to track the movements of different parts of the body during walking) and we aim to characterise this in a small number of children with MPS IVa and also examine the effects of splinting the wrist upon the walking pattern to see if this simple intervention makes it easier or more difficult for children with MPS IVa to walk.

Inclusion Criteria:

• Confirmed diagnosis of MPS IVa (documented history of reduced leucocyte GALNS enzyme activity relative to the normal range of the laboratory performing the assay AND/OR molecular analysis showing two pathogenic mutations in the GALNS gene)
• Willing and able to provide written assent and parent/legal guardian able to provide written informed consent after the nature of the study has been explained and prior to any research-related procedures
• Between 6 and 18 years of age inclusive
• Willing to perform all study procedures as far as physically possible

Exclusion Criteria:

• Inability to comply with Gait Analysis protocol (e.g. nonambulant)
• Recent orthopaedic surgery that investigator deems might impact on Gait Analysis
• Use of any investigational product or investigational medical device other than BMN110 within 30 days prior to recruitment, or requirement for any investigational agent other than BMN110 prior to completion of all scheduled study assessments
• Concurrent disease or condition that would interfere with study participation or safety
• Any condition that, in the view of the Principal or Subinvestigators, places the subject at high risk of not completing the study procedures