MPS I – Skeletal System

Skeletal and joint manifestations represent the most significant disability and discomfort for patients with MPS I.^[1] In severe cases, skeletal involvement in MPS I patients can be detected in the first year of life by radiological methods.^{[1, 2]} Clinically, skeletal involvement does not usually become obvious until the age of 10-14 months when a gibbus deformity of the back, or dorsolumbar kyphosis, is observed. Eventually, progressive skeletal dysplasia involving all bones is seen in all patients.

Interphalangeal joint involvement along with carpal tunnel syndrome commonly lead to poor hand function.^{[1, 2]} Diagnosis of carpal tunnel syndrome is often missed because its onset is insidious and often presents with few or no symptoms except thenar atrophy. Patients should be evaluated for this, as they may benefit from carpal tunnel release.

Kyphosis, scoliosis, and severe back pain are also common in MPS I patients. Progressive arthropathy affecting all joints, and eventually leading to the loss of, or severe restriction of, range of motion is universal.

MPS I is associated with different degrees of growth retardation, typically involving the trunk more than the limbs.

References

1. Clarke, L.A. (1997) Clinical diagnosis of lysosomal storage diseases. In: Organelle Diseases. Clinical Features, Diagnosis, Pathogenesis and Management. Applegarth, D.A., Dimmick, J.E., and Hall, J.G. (eds.). Chapman and Hall Medical, London, pp. 37.

2. Neufeld, E.F., and Muenzer, J. (2001) The mucopolysaccharidoses. In: The Metabolic and Molecular Bases of Inherited Disease. Scriver, C.R., Beaudet, A.L., Sly, W.S., Valle, D., Childs, B., Kinzler, K.W., and Vogelstein, B. (eds.). 8th edition, Vol. III. McGraw-Hill, Medical Publishing Division, pp. 3421.