Hunter disease is an X-linked lysosomal storage disorder characterized by progressive storage of glycosaminoglycans (GAGs) and multi-organ impairment. The central nervous system (CNS) is involved in at least 50% of cases. Since 2006, the enzymatic replacement therapy (ERT) is available but with no effect on the cognitive impairment, as the present formulation does not cross the blood–brain barrier. Here we report the outcome of 17 Hunter patients treated in a single center. Most of them (11) started ERT in 2006, 3 had started it earlier in 2004, enrolled in the phase III trial, and 3 after 2006, as soon as the diagnosis was made. The liver and spleen sizes and urinary GAGs significantly decreased and normalized throughout the treatment. Heart parameters improved, in particular the left ventricular mass index/m2 decreased significantly. Amelioration of hearing was seen in many patients. Joint range of motion improved in all patients. However, no improvement on respiratory function, eye, skeletal and CNS disease was found. The developmental quotient of patients with a CNS involvement showed a fast decline. These patients were no more testable after 6 years of age and, albeit the benefits drawn from ERT, their quality of life worsened throughout the years. The whole group of patients showed a consistent residual disease burden mainly represented by persistent skeletal disease and frequent need of surgery. This study suggests that early diagnosis and treatment and other different therapies which are able to cross the blood–brain barrier, might in the future improve the MPS II outcome.

Mucopolysaccharidoses (MPS) are a group of diseases characterized by abnormal accumulation of glycosaminoglycans (GAGs). Although there are differences among the various disease types, the osteoarticular system is always involved. The aim of the present study was to establish a framework for MPS-related orthopaedic manifestations and for their treatment. The authors, affiliated to three different Italian Orthopaedic Centres, report data taken from the literature reviewed in light of their accumulated professional experience. Bone alterations make up what is known as dysostosis multiplex, involving the trunk and limbs and with typical radiological findings. Joints are affected by pathological tissue infiltrations. The cervical spinal cord is involved, with stenosis and cervical and occipitocervical instability. In MPS there is a much higher incidence of scoliosis compared with healthy subjects without any particular distinctive feature. Kyphosis of the spine is more frequent and also more severe because of its possible neurological complications, and it is localized at the thoracolumbar level with a malformed vertebra at the top of the deformity. Evolving forms, and those associated with neurological damage, require anteroposterior spine fusion. The hip is invariably involved, with dysplasia affecting the femoral neck (coxa valga), the femoral epiphysis (loss of sphericity, osteonecrosis), and the femoral acetabulum which is flared. All these features explain the tendency to progressive hip migration. Genu valgum is often found (a deviation of the physiological axis with an obtuse angle opening laterally). This deformity is often localized at the proximal tibial metaphysis; it causes functional limitations and leads to an irregular erosion of the articular cartilage. In young patients who still have the growth plate, it is possible to execute a medial hemiepiphysiodesis, a temporary inhibition of cartilage growth, with progressive axis correction. In this paper, the characterisation of clinical features and the review of treatments are divided into separate sections based on the part of the body involved. The conclusions of each section are presented as a summary. One section discusses the high risk of anaesthesia-related complications requiring the collaboration of specifically trained personnel.

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