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Patient with coarse facies and quadriparesis

Mucopolysaccharidoses

Inherited lysosomal storage disorders

Inability to break down glycosaminoglycans (GAG) leading to intracellular accumulation and toxicity

Location

Spine: CVJ, thoracolumbar spine, pelvis

Odontoid soft tissue mass varies from small to large (usually in older patients)

Skull base thickening, occipital hypoplasia, short posterior arch C1, odontoid hypoplasia +/- os odontoideum, ligamentous laxity, dural thickening with spinal stenosis, atlantoaxial instability

Thoracolumbar spine- kyphosis, kyphoscoliosis

Platyspondyly, anterior beaking of vertebral bodies, thoracolumbar gibus deformity (MPS 1-H and IV)

Extraspinal: Brain, visceral organ deposition

Radiographic Findings

CT

Odontoid dysplasia +/- atlantoaxial subluxation

Dysplastic blunted spinous processes, wedged vertebral bodies, spinal canal stenosis

CVJ central and foraminal narrowing, dural thickening

Abnormal dens ossification with laminar thickening and enlarged medullary cavity

MRI

T1 Hypo to Isointense peri-odontoid soft tissue mass, hypointense thickened dura

T2 Hypoplastic dens and peri-odontoid soft tissue mass, thickened dura +/- cyst formation due to meningeal thickening +/- cord compression with hyperintense signal abnormality

T1+c no abnormal enhancement, even if odontoid mass present

Differential Diagnosis

GM1 gangliosidosis

Has features of vertebral beaking, upper lumbar gibbus and dens hypoplasia

Distinguished on clinical, genetic criteria

Mucolipidosis (pseudo-Hurler polydysrophy)

Has features of vertebral beaking, upper lumbar gibbus and dens hypoplasia

Distinguished on clinical, genetic criteria

Achondroplasia

Autosomal dominant disorder of endochondral bone

Short broad pedicles and thickened laminae

Distinguished on genetic criteria

Down syndrome

+/- Dens hypoplasia without soft tissue dens mass or marrow deposition features

Distinguished on clinical, genetic criteria

Spondyloepiphyseal dysplasia

Autosomal dominant / presents at birth

Flattening of vertebral bodies, dens hypoplasia, scoliosis

Minimal hand and foot involvement

Pathology

Glycosaminoglycans accumulates in most organs and ligaments

Coarse facies

Hepatosplenomegaly, umbilical hernia

Skeletal dysostosis multiplex, joint contractures

Arterial walls, mid aortic stenosis, cardiac valve thickening

Upper airway obstruction

Odontoid hypoplasia, GAG deposition with +/- ligamentous laxity with reactive change produce soft tissue mass around dens

Biconvex ovoid, bullet shaped or rectangular vertebral bodies, vertebral beaking

Autosomal Recessive except MPS II Hunter’s

Inherited lysosomal enzyme deficiency

CVJ stenosis=neurovascular compression, altered CSF dynamics=hydocephalus, hydrosyringomyelia

Dilated enlarge laminae medullary cavities

Dural thickening due to mucopolysaccharide deposition with elastic and collagenous proliferation

Classification

Hurler (MPS 1-H) alpha-l-iduronidase

Hunter (MPS II) Iduronase 2-sulfatase

Sanfillipo (MPS III) Heparin N-sulfatase

Morquio (MPS IV) Galactose 6-sulfatase

Most common 1:40,000 births

Scheie (MPS V)

Maroteaux-Lamy (MPS VI) Arylsulfatase B

Sly (MPS VII)

Clinical

Subtle progressive myelopathy / reduced exercise tolerance

Coarse facies, macroglossia, bushy eyebrows, flat nasal bridge

Corneal clouding except MPS II

Mental retardation except MPS I H/S, IIb, and IV

Joint contractures, dysostosis multiplex

Natural History

Premature death

Slowly progressive cord decompression= quadriparesis

Apnea and sudden death may follow minor trauma

Treatment

Posterior occipitocervical decompression/stabilization

Transoral odontoid resection/posterior stabilization

Bone marrow transplant or intravenous recombinant human enzyme

Decreased GAG accumulation in organs