Assessment of bone mineral density by dual energy x-ray absorptiometry in patients with mucopolysaccharidoses

BACKGROUND: Patients with mucopolysaccharidoses (MPS) are associated with poor bone growth and mineralization, however, information regarding the assessment of bone mineral density (BMD) in relation to age and treatment in this disorder is limited. METHODS: Dual energy x-ray absorptiometry (DXA) was performed in 30 patients with MPS (21 males and 9 females; 2 with MPS I, 12 with MPS II, 2 with MPS IIIB, 9 with MPS IVA, and 5 with MPS VI; median age, 10.8 years; age range, 5.0 years to 23.7 years; 26 patients were under 19 and 4 were above 19 years of age) to assess BMD of the lumbar spine (L1-L4), using the Hologic QDR 4500 system (Bedford, MA, USA). RESULTS: For 26 patients under 19 years of age, standard deviation scores (z scores) for height, weight, body mass index (BMI), and BMD were −4.53 ± 2.66, -1.15 ± 1.55, 0.74 ± 1.23, and −3.03 ± 1.62, respectively, and they were all negatively correlated with age (p < 0.05). However, after correction for height-for-age z score (HAZ), HAZ adjusted BMD z score was −0.7 ± 1.24. Eight patients (31%) had osteopenia (HAZ adjusted BMD z score < −1 and ≥ −2), and 4 patients (15%) had osteoporosis (HAZ adjusted BMD z score < −2). Of 8 patients with MPS I, II or VI who underwent follow-up DXA after receiving enzyme replacement therapy for 1.0 to 7.4 years, all showed increase in absolute BMD values. CONCLUSIONS: These findings and the follow-up data can be used to develop quality of care strategies for patients with MPS.