The Hip in Mucopolysaccharidoses

Abstract

The mucopolysaccharidoses (MPSs) are a group of lysosomal storage disorders (LSDs) characterized by a genetic deficiency or dysfunction of the enzymes required to breakdown glycosaminoglycans (GAGs). Unmetabolized GAG molecules accumulate in the intracellular and extracellular spaces throughout the body, affecting multiple organ systems. Current metabolic treatment consists of Hematopoetic Stem Cell Transplantation (HSCT) in Hurler Syndrome (MPS I-H), as well as Enzyme Replacement Therapy (ERT) in other MPS conditions. MPS I-H is the archetype of MPS conditions. The constellation of musculoskeletal abnormalities seen in the MPSs is termed “dysostosis multiplex”. In the hip, this is characterized by acetabular dysplasia that is due to decreased ossification of the lateral portion of the acetabulum. However, the unossified cartilaginous anlage of the acetabulum is still present. Progressive coxa valga in the latter half of the first decade may lead to progressive hip subluxation. In patients in whom the hips are not treated, many patients develop hip pain, stiffness and disability in the second decade of life. Hip reconstructive surgery, if performed, requires combined femoral varus osteotomies and pelvic osteotomies. The role of early hip reconstructive surgery still requires further study to determine its efficacy and impact on future hip function and quality of life.