Clinical presentation and follow-up of patients with the attenuated phenotype of mucopolysaccharidosis type I

Aim: To review the heterogeneity and severity of the clinical features at the attenuated end of the mucopolysaccharidosis (MPS) type I disease spectrum. Methods: The course of disease in 29 patients with attenuated mucopolysaccharidosis I who attended the MPS clinic in Manchester, UK, was reviewed. Results: For more than half of the patients, onset of symptoms was in the first 2 y of life, and the age at diagnosis ranged from 15 mo to 40 y. Joint stiffness, corneal clouding, umbilical hernia and recurrent ear, nose and throat symptoms were the commonest features at presentation. Patients experienced significant morbidity during the course of this inherited disease. Skeletal problems predominated and cardiac valve pathology, upper airway obstruction and hearing deficits were detected in a notable number of patients. Nerve decompression for carpal tunnel syndrome, cervical cord decompression, and grommet insertion for serous otitis media were the most frequent surgical interventions. Conclusion: Clinical presentation of attenuated ("non-Hurler") mucopolysaccharidosis type I is heterogeneous in time of onset and types of clinical features. A better understanding of the spectrum of disease and of the related disease progression will contribute to more accurate diagnosis, and patients will benefit from early intervention.