Principes des approches thérapeutiques pour les mucopolysaccharidoses

Comparison of dermatan sulfate and heparan sulfate concentrations in serum, cerebrospinal fluid and urine in patients with mucopolysaccharidosis type I receiving intravenous and intrathecal enzyme replacement therapy

AIMS

To validate a liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the measurement of glycosaminoglycans (GAGs) in plasma and serum. To establish plasma, cerebrospinal fluid (CSF) and urine reference intervals. To compare GAGs in serum with that in urine and CSF from patients with MPS I.

METHODS

Dermatan sulfate (DS), heparan sulfate (HS), and chondroitin sulfate (CS) in serum/plasma, urine and CSF were methanolysed into dimers and analyzed using pseudo isotope dilution UPLC-MS/MS assay. Serum, CSF and urine DS and HS were quantified for 11 patients with mucopolysaccharidosis (MPS) type I before and after treatment with Aldurazyme® (laronidase) enzyme replacement therapy (ERT).

RESULTS

The method showed acceptable imprecision and recovery for the quantification of serum/plasma CS, DS, and HS. The serum, urine, and CSF DS and HS concentrations were reduced after 26 weeks of ERT in 4 previously untreated patients. Serum DS and HS concentrations normalized in some patients, and were mildly elevated in others after ERT. In contrast, urine and CSF DS and HS values remained elevated above the reference ranges. Compared with serum GAGs, urine and CSF DS and HS were more sensitive biomarkers for monitoring the ERT treatment of patients with MPS I.

Spine challenges in mucopolysaccharidosis

PURPOSE

Mucopolysaccharidosis (MPS) are rare inherited metabolic diseases, causing lysosomal storage of mucopolysaccharides; clinical presentation involves skeletal system and particularly the spine. Anomalies include developing kyphosis at thoracolumbar junction, that can causes nervous symptoms, and dens hypoplasia with associated atlantoaxial subluxation that can cause myelopathy. We present our experience in the treatment of spine pathology in MPS.

METHODS

Medical treatments of MPS seem to have little impact on spine disease: treatment of cervical instability often includes surgical decompression and stabilization, as in patient MPS1 that we present, while thoracic lumbar kyphosis is treated by bracing and, in severe cases, with surgery. Bracing is more effective in kyphosis under 40° Cobb. Our surgical cases with thoracic lumbar kyphosis over 40° Cobb, treatment include the first one ever described by only posterior approach with vertebrectomy in MPS and a case of lateral costo-transverse approach instrumented correction.

RESULTS

Surgical patients had no major complications after surgery and CT scan at follow-up showed complete fusion without loss of correction, even if in a cervical case we used an adult rigid instrumentation in a four year-and-six month-old girl (11 years follow-up) and in thoracic lumbar kyphosis case treated by vertebrectomy due to diminutive anatomy we positioned interbody cage in suboptimal position.

CONCLUSIONS

Bracing is a viable treatment strategy in thoracic lumbar kyphosis and can obtain good clinical results at medium terms follow-up even if kyphosis deformity remains in radiographs. Surgical treatment is effective in severe evolving cases both at cervical and thoracic lumbar level, main difficulties arose from unavailability of dedicated instrumentation in very young patient, as even smallest devices available are often too big.

Spinal involvement in mucopolysaccharidoses: a review

BACKGROUND

Mucopolysaccharidoses (MPS) represent a group of inheritable lysosomal storage diseases caused by mutations in the genes coding for enzymes involved in catabolism of different glycosaminoglycans (GAGs). They are clinically heterogeneous multisystemic diseases, often involving the spine. Bony abnormalities of the spine included in the so-called dysostosis multiplex and GAG deposits in the dura mater and supporting ligaments can result in spinal cord compression, which can lead to compressive myelopathy. Spinal involvement is a major cause of morbidity and mortality in some MPS (e.g., MPS IVA, VI, and I), and early radiological diagnosis is critical in preventing or arresting neurological deterioration and loss of function.

DISCUSSION

Management of MPS, however, requires a multidisciplinary approach because of the multiorgan nature of the disease. Indeed in order to appreciate the relevance and nuances of each other's specialty, radiologists and clinicians need to have a background of common knowledge, rather than a merely compartmentalized point of view. In the interest of the management of spinal involvement in MPS, this review article aims on one hand to provide radiologists with important clinical knowledge and on the other hand to equip clinicians with relevant radiological semiotics.