Mucopolysaccharidoses (MPS) are rare genetic diseases caused by the deficiency of one of the lysosomal enzymes involved in the glycosaminoglycan (GAG) breakdown pathway. This metabolic block leads to the accumulation of GAG in various organs and tissues of the affected patients, resulting in a multisystemic clinical picture, sometimes including cognitive impairment. Until the beginning of the XXI century, treatment was mainly supportive. Bone marrow transplantation improved the natural course of the disease in some types of MPS, but the morbidity and mortality restricted its use to selected cases. The identification of the genes involved, the new molecular biology tools and the availability of animal models made it possible to develop specific enzyme replacement therapies (ERT) for these diseases. At present, a great number of Brazilian medical centers from all regions of the country have experience with ERT for MPS I, II, and VI, acquired not only through patient treatment but also in clinical trials. Taking the three types of MPS together, over 200 patients have been treated with ERT in our country. This document summarizes the experience of the professionals involved, along with the data available in the international literature, bringing together and harmonizing the information available on the management of these severe and progressive diseases, thus disclosing new prospects for Brazilian patients affected by these conditions.

In mucopolysaccharidosis I, deficiency of alpha-L-iduronidase can cause spinal cord compression (SCC) due to storage of glycosaminoglycans (GAGs) within the cervical meninges. As intravenous enzyme replacement therapy (ERT) is not likely to provide enzyme across the blood-brain barrier, standard treatment for this complication is usually surgical, which has a high morbidity and mortality risk. We report on the use of intrathecal (IT) laronidase in a MPS I patient with SCC who refused the surgical treatment. Assessments were performed at baseline, with clinical and biochemical evaluations, 4-extremity somatosensory evoked potentials, 12 min walk test and MRI studies of the CNS. Changes on these parameters were evaluated after 4 IT infusions of laronidase administered monthly via lumbar puncture. To our knowledge, this was the first MPS patient who received IT ERT. No major adverse events were observed. There were no clinically significant changes in serum chemistries. CSF GAG results revealed pretreatment values slightly above normal standards: 13.3 mg/L (NV < 12 mg/L) which after IT laronidase infusions were within normal levels (10.3 mg/L). 12MWT presented a 14% improvement, with better performance on stability and gait control. Maximum voluntary ventilation showed 55.6% improvement considering the percentage of predicted (26.7% at baseline compared to 41.9%); Maximum Inspiration Pressure improved 36.6% of predicted (26.8% at baseline to 36.7%); Pulmonary diffusion improved 17.6% of predicted %. In conclusion, although the improvement observed in this case with IT laronidase should be confirmed in further patients, this procedure seems to be a safe treatment for SCC in MPS I.

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