The muscle-bone relationship in X-linked hypophosphatemic rickets

Area of Science:

• Orthopedics
• Pediatrics
• Endocrinology

Background:

• X-linked hypophosphatemic rickets (XLH) is associated with lower extremity muscle function deficits.
• Bone mass and muscle force are typically correlated, prompting investigation into potential bone deficits in XLH.

Purpose of the Study:

• To investigate the relationship between muscle and bone in the lower extremities of patients diagnosed with XLH.
• To determine if XLH patients, despite muscle deficits, also present with reduced bone mass.

Main Methods:

• A comparative study involving 30 XLH patients and 30 age/gender-matched controls.
• Peripheral quantitative computed tomography (pQCT) used to assess calf muscle size/density and tibia bone mass/geometry.
• Muscle function evaluated via peak force during a 2-legged hopping test.

Main Results:

• XLH patients demonstrated significantly lower muscle force compared to controls.
• Muscle cross-sectional area was comparable between groups after adjusting for tibia length.
• XLH patients exhibited significantly larger external bone size and higher bone mineral content in the tibia.

Conclusions:

• Patients with X-linked hypophosphatemic rickets present with increased bone mass and size in the distal tibia.
• These bone changes occur concurrently with observed muscle function deficits in the lower extremities.