Functional capacity evaluation of patients with mucopolysaccharidosis

The mucopolysaccharidoses (MPS) are rare genetic disorders caused by a deficiency in lysosomal enzymes that affect the catabolism of glycosaminoglycans and cause their accumulation, resulting in a multisystemic clinical picture. Their clinical manifestations result in limited ability to perform daily life tasks.

To evaluate functional capacity and joint range of motion (ROM) in patients with MPS followed at the reference center for lysosomal disorders at Hospital de Clínicas de Porto Alegre, Brazil.

This was a prospective longitudinal study with a convenience sample. The Pediatric Evaluation of Disability Inventory (PEDI) and the Functional Independence Measure (FIM) were used to evaluate functionality and goniometry was used to evaluate ROM at three times (baseline, 6 months, and 12 months after study inclusion). An exploratory analysis was done of the effect of enzyme replacement therapy (ERT) in both variables; thus, patients were divided into Group 1 (patients without ERT), Group 2 (patients on ERT before and after study inclusion), and Group 3 (patients who started ERT after study inclusion).

21 patients were included: 7 in Group 1 (MPS II: 3, MPS III-B: 2, MPS IV-A: 2), 6 in Group 2 (MPS I: 3; MPS VI: 3), and 8 in Group 3 (MPS I: 3, MPS II: 4, MPS VI: 1). A limitation in the mobility of all joints studied was found especially in MPS I, II, and VI. Functionality compromise was also frequent (PEDI=5/7 patients; MIF=9/14 patients), even in individuals with preserved cognition. No correlation was found between the findings of goniometry and the PEDI domains (self-care, mobility, social function). ERT did not seem to significantly change the parameters analyzed.

The compromise of joint mobility and functionality seems to be common in MPS I, II, III-B, IV-A, and VI. This finding is in line with the fact that, although these types of MPS are caused by different genetic defects, they share metabolic routes and physiopathogenic processes and present similar clinical manifestations. The preservation of functionality is an increasing challenge in the treatment of MPS patients, and maintenance of occupational performance should be defined as an objective to be reached by therapies used. Further studies with a greater sample size are necessary in order to verify the effect of ERT in these variables.