Bone mineral density in mucopolysaccharidosis IVB

Area of Science:

• Medical Science
• Genetics
• Metabolic Disorders

Background:

• Mucopolysaccharidosis type IV (MPS IV) is a rare genetic disorder.
• Previous bone mineral density (BMD) studies in MPS IV focused only on MPS IVA.
• No published data exists on BMD for MPS IVB patients.

Purpose of the Study:

• To prospectively evaluate BMD in patients with MPS IVB.
• To identify reliable measurement sites for BMD assessment in MPS IVB.
• To correlate BMD findings with functional abilities and medical history.

Main Methods:

• Prospective study of three MPS IVB patients (aged 17.7, 31.4, 31.7 years).
• Dual-energy X-ray absorptiometry (DXA) used for BMD measurement at whole body (WB), lumbar spine (LS), and lateral distal femur (LDF).
• Evaluation of functional abilities, ambulatory status, medical history, and height z-score.

Main Results:

• WB and hip DXA scans were invalid in all patients due to prosthetic hardware.
• LS BMD measurement was valid in only one patient due to skeletal abnormalities.
• LDF BMD was consistently measurable and revealed low bone density across all regions (average Z-scores: -3.1, -2.3, -2.1).
• All patients were ambulatory, and one experienced trauma-related fractures.

Conclusions:

• Patients with MPS IVB exhibit low BMD in lower extremities despite full-time ambulation.
• Standard DXA sites (WB, hip, LS) present challenges for BMD assessment in MPS IVB.
• The LDF is identified as a consistently available and reliable site for BMD measurement in MPS IVB patients.
• Absence of low-energy fractures despite low BMD warrants further investigation.