Long-term outcomes of enzyme replacement therapy from a large cohort of Korean patients with mucopolysaccharidosis IVA (Morquio A syndrome).

Mucopolysaccharidosis (MPS) IVA (Morquio A syndrome) is an autosomal recessive lysosomal storage disorder caused by a mutation affecting the enzyme N-acetylgalactosamine-6-sulfatase (EC 3.1.6.4, GALNS). Enzyme replacement therapy (ERT) has been shown to improve physical performance, quality of life, and respiratory function in patients with MPS IVA; however, owing to the rarity of MPS IVA, data on Korean patient characteristics are limited. This retrospective study reports clinical, radiographic, biochemical, and molecular findings, and analyzes long-term clinical outcomes, from the largest cohort of Korean patients with MPS IVA in a single center. The analysis included 17 patients from 14 families (58.8 % females; median [range] age at diagnosis 5.2 [1.8-33.7] years). The majority of patients (64.7 %) were classified as having a severe phenotype, 23 % had an intermediate phenotype, and 11.8 % had an attenuated phenotype. Skeletal manifestations and radiologic abnormalities at initial diagnosis included gait abnormality (35.3 %), short stature (23.5 %), chest deformity (23.5 %), scoliosis (17.6 %), kyphosis (11.8 %), dysmorphic face (6 %), hip pain (6 %), and leg deformity (6 %). Twelve different GALNS mutations were identified. Patients received ERT for a median (range) 7.4 years (3.0-12.1). Twelve patients reached final adult height, and all patients with the severe/intermediate phenotype had short stature (<3rd percentile). Hemiepiphysiodesis was the most common surgical intervention among patients with the severe/intermediate phenotype. Drug-related adverse events (urticaria, rash, and anaphylaxis) were reported in four patients but were managed with antihistamines or desensitization. At follow-up, patients experienced improvements in functional independence measure score, ejection fraction, and the 6-min walk test compared with the pre-treatment baseline. This study provides real-world evidence for long-term stabilization of functional independence, endurance, and respiratory function among patients with MPS IVA treated with ERT, with no new safety concerns identified.