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Case Seventy Two - Hunter's Syndrome
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Clinical History: Teenager being evaluated for pneumonia.
Findings: Chest x-ray obtained to evaluate for pneumonia shows no infiltrate. Evaluation of the bones of this patient demonstrate broad ribs which taper posteriorly. Additionally, the clavicles are short and broad.
Diagnosis: Hunter’s syndrome.
Discussion: Hunter’s syndrome is one of the seven described mucopolysaccharidoses, which are glycosaminoglycan deposition diseases which result from specific inherited lysosomal enzyme deficiencies. The clinical features of the different mucopolysaccharidoses are variable, each subtype having a characteristic pattern of organ involvement and severity. Ultimately, specific diagnosis is based upon genetic markers, enzyme assay and/or analysis of glycosaminoglycans excreted in the urine.
The characteristic pattern of skeletal involvement seen in the mucopolysaccharadoses (as well as the mucolipidoses, which are also lysosomal storage disorders) has been termed "dysostosis multiplex". Abnormalities seen in dysostosis multiplex include the following:
- SKULL: dolichocephaly secondary to premature closure of he sagittal sutures,
underdevelopment of paranasal sinuses and mastoid air cells, J-shaped sella
turcica, thick diploic space, malformed teeth.
- SPINE: vertebral body underdevelopment, especially anterosuperiorly, leading to
a hook or oval shape, gibbus deformity at the thoracolumbar junction.
- CHEST: oar-shaped or paddle-shaped ribs which are broad with tapering
posteriorly, clavicles which are broad and short, small scapulae.
- PELVIS: increased acetabular angles secondary to underdevelopment
superolaterally, coxa valga, delayed and dysplastic femoral head development.
- LONG BONES: diaphyseal and metaphyseal expansion, delayed ossification
centers, cortical thinning. The upper extremities are affected more severely than
the lower extremities.
- HANDS: short and wide phalanges which taper distally ("bullet shaped"), cortical
thinning, deformed carpal bones, altered carpal angle.
The skeletal manifestations of Hunter’s syndrome tend to be moderate in severity while those of Hurler’s and Morquio’s syndromes tend to be more severe. While the skeletal changes seen in this group of syndromes can be marked, often leading to grotesque features and dwarfism, it is involvement of other organ systems such as the heart and central nervous system which often produce significant morbidity and mortality in affected patients.
References:
- Chen S, et al. "Bony Changes in Common Mucopolysacchardoses",
Acta Paed Sin, 1996;37(3):178-184.
- Resnick D, et al. Diagnosis of Bone and Joint Disorders, 2nd edition.
W.B. Saunders Company, 1988, pages 3501-3506.
- Taybi H, et al. Radiology of Syndromes, Metabolic Disorders and Skeletal
Dysplasias, fourth edition. Mosby, pages 370-681.
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Submitted by:
Richard Hasson, M.D.
Melissa Myers, M.D.
