Early response to idursulfase treatment in a 3 year-old boy affected of Hunter syndrome.

Department of Pediatrics, Hospital Materno-Infantil-Hospital Infanta Cristina, Facultad de Medicina, Avda Damian Tellez Lafuente s/n, 06010 UEX Badajoz, Spain
European Journal of Medical Genetics (Impact Factor: 1.49). 05/2008; 51(3):268-71. DOI: 10.1016/j.ejmg.2008.02.005
Source: PubMed

ABSTRACT We present a 3-year-old boy affected with Hunter syndrome. When we first evaluated the patient glycosaminoglycans (GAG) in urine were elevated (94.6 ng/nmol/creatinine); the enzyme activity determined in serum was decreased (3.9 nmol/hxml) and the mutation found was N350H, exon 8. His clinical signs were coarse facial features, hepatomegaly (6 cm), splenomegaly (6 cm), elbow stiffness and hypospadias; dilatation of the perivascular spaces and white matter abnormalities, mitral regurgitation. After two weeks on enzyme replacement therapy (ERT) with idursulfase (IDS), the excretion of GAG was decreased to 36.2 ng/nmol/creatinine and the liver and spleen volumes were reduced to normal limits. He was subsequently noted to have a softer, finer skin, he had no further bouts of bronchitis, and his physical activity improved. This indicates that IDS in young children is well tolerated and that it has several effects which may confer clinical benefits with long-term therapy.

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    ABSTRACT: Intravenous enzyme replacement therapy (ERT) with idursulfase for Hunter syndrome has not been demonstrated to and is not predicted to cross the blood-brain barrier. Nearly all published experience with ERT with idursulfase has therefore been in patients without cognitive impairment (attenuated phenotype). Little formal guidance is available on the issues surrounding ERT in cognitively impaired patients with the severe phenotype. An expert panel was therefore convened to provide guidance on these issues. The clinical experience of the panel with 66 patients suggests that somatic improvements (e.g., reduction in liver volume, increased mobility, and reduction in frequency of respiratory infections) may occur in most severe patients. Cognitive benefits have not been seen. It was agreed that, in general, severe patients are candidates for at least a 6-12-month trial of ERT, excluding patients who are severely neurologically impaired, those in a vegetative state, or those who have a condition that may lead to near-term death. It is imperative that the treating physician discuss the goals of treatment, methods of assessment of response, and criteria for discontinuation of treatment with the family before ERT is initiated. CONCLUSION: The decision to initiate ERT in severe Hunter syndrome should be made by the physician and parents and must be based on realistic expectations of benefits and risks, with the understanding that ERT may be withdrawn in the absence of demonstrable benefits.
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    ABSTRACT: Hunter syndrome or mucopolysaccharidosis II (MPS II) is a rare X-linked disease caused by a deficiency of the iduronate-2-sulphatase (12S) lysosomal enzyme, resulting in a progressive accumulation of glycosaminoglycans (GAGs). Enzyme replacement therapy (ERT) with recombinant human 12S idursulfase has been used infrequently in children < 5 years. We present the case of a 7 years and 10 months-old child, who was diagnosed with a severe form of MPS II at the age of 3 years, and who began a 36 months' treatment with idursulfase at 4 years 10 months. After 10 months, GAG urinary excretion was normal, but after just 4 months the liver and spleen had decreased in size, returning to normal limits by 36 months. Significant bone remodeling was noted after 16 months. Cardiac and neurological development, however, progressively deteriorated. The only adverse reactions were episodic inflammations of the upper and/or lower respiratory tract, but there was no otitis. Early use of ERT, presuming good treatment adherence, can significantly improve bone abnormalities.
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    ABSTRACT: The Hunter syndrome (HS), or mucopolysaccharidosis type ii, is a disease caused by a deficiency or absence of the enzyme iduronate-2-sulfatase (I2S) due to mutations in the IDS gene. I2S deficiency causes a block in the degradation of glycosaminoglycans (GAG) in cytoplasmic lysosomes which leads to their accumulation in cells. This causes a generalized cellular disorder and increased elimination of these GAG in urine. The HS is an inherited X-linked recessive disease, which affects one in 49,000 to 526,000 male live births. The HS progressive and multisystem involvement usually causes the need of various medical specialties for managing the disease. Recently a new enzyme replacement therapy with recombinant I2S is available, which improves and slows the disease progression. Thus, early diagnosis and treatment are key factors for managing HS. For these reasons, this clinical practice guideline (CPG) has been developed. This CPG aims to help the different specialists who manage patients with SH in the early detection, follow-up and treatment. This guide has been developed by a working group set up by the Spanish Hunter Group (multidisciplinary team of physician specialists in the diagnosis and management of HS) and researchers with methodological experience in developing GPC. The recommendations are based on the synthesis of the best available scientific evidence and the experience of experts.
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