BACKGROUND/OBJECTIVE: Quantitative urine screening for mucopolysaccharides (MPS) has been the primary method for detecting mucopolysaccharidoses in children. This method may not be sufficiently sensitive and may miss some patients with arylsulfatase B (ARSB) deficiency. Investigators propose to identify patients retrospectively and prospectively who carry a diagnosis of spondyloepiphyseal dysplasia, multiple epiphyseal dysplasia, bilateral proximal femoral epiphyseal dysplasia, or bilateral Legg-Calve-Perthes. For these patients, investigators will perform enzyme testing on a blood sample which will identify MPS VI or IVA.

Patients who have an earlier diagnosis of MPS are likely to have better health outcomes with medical management. Therefore, it is important to determine effective diagnostic methods. Investigators believe that bilateral hip involvement should alert the clinician to the possibility of MPS VI and further examination. The purpose of this study is to test the hypothesis that the correct diagnoses of two MPS storage disorders are delayed in patients with bilateral proximal femoral epiphyseal dysplasia and normal quantitative urine MPS studies.

Inclusion Criteria:

• Less than or equal to 21 years of age
• Diagnosis of spondyloepiphyseal dysplasia or multiple epiphyseal dysplasia or bilateral Legg-Calve-Perthes disease or bilateral proximal femoral epiphyseal dysplasia.

Exclusion Criteria:

• Definitive etiology for above-mentioned diagnosis (i.e. other MPS disease, known chondrodysplasia, Meyer's dysplasia)

Males/females less than or equal to 21 years of age who have been seen at Gillette Children's Specialty Healthcare or Children's Hospitals and Clinics of Minnesota and carry a diagnosis of spondyloepiphyseal dysplasia or multiple epiphyseal dysplasia or bilateral Legg-Calve-Perthes disease or bilateral proximal femoral epiphyseal dysplasia.