Characterization of pulmonary function impairments in patients with mucopolysaccharidoses—changes with age and treatment

Abstract

BACKGROUND: The mucopolysaccharidoses (MPS) comprise a group of inherited lysosomal storage disorders characterized by deficiencies in enzymes catalyzing the degradation of glycosaminoglycans. Impairment of pulmonary function is an important health problem for patients with MPS. However, there are few published reports on the prevalence and severity of pulmonary dysfunction in relation to age and treatment in this disorder. METHODS: To evaluate pulmonary function in patients with MPS, we performed spirometry in 35 patients (22 males and 13 females; 1 with MPS I, 12 with MPS II, 16 with MPS IVA, and 6 with MPS VI; mean age, 14.6 ± 5.9 years; age range, 6.4 years to 33 years). Forced vital capacity (FVC), forced expired volume in 1 sec (FEV1), FEV1 to FVC ratio (FEV1/FVC), peak expiratory flow (PEF), and mean forced expiratory flow during the middle half of FVC (FEF25-75% ) were measured. RESULTS: Mean FVC, FEV1 , PEF, and FEF25-75% were 74.2%, 73.9%, 64.7%, and 37.1% of the predicted values, respectively. By spirometric classification, 32 patients (91%) had small airway disease (FEF25-75% < 65%), 17 (48%) had restrictive lung disease, and 3 (9%) had obstructive lung disease. Percent predicted FVC, FEV1 , and PEF, as well as FEV1 /FVC, were all negatively correlated with age (P < 0.01), such that pubertal and post-pubertal patients had significantly lower values than younger patients. Of eight attenuated MPS II and VI patients who underwent follow-up pulmonary function testing after receiving enzyme replacement therapy (ERT) for 1.5-7.4 years, six showed improvements in % predicted FVC and five improved in % predicted FEV1 . CONCLUSION: Our additional characterization of the types and prevalence of pulmonary function abnormalities seen in MPS patients should be useful for clinical care.