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  • Open Access

Mc Cune Albright syndrome: estimation of bone strength parameters and response to treatment using peripheral Quantitive Computed Tomography (pQCT) of the tibia

  • 1Email author,
  • 1,
  • 1,
  • 2,
  • 2,
  • 1,
  • 1,
  • 2 and
  • 2
Pediatric Rheumatology20119 (Suppl 1) :P27

https://doi.org/10.1186/1546-0096-9-S1-P27

  • Published:

Keywords

  • Fibrous Dysplasia
  • Precocious Puberty
  • Peripheral Quantitative Compute Tomography
  • Polyostotic Fibrous Dysplasia
  • GNAS1 Gene

Aim

We assessed bone strength parameters and response to treatment in a girl with McCune -Albright syndrome (MAS) using tibia pQCT.

Methods

We present a 14y old girl with polyostotic fibrous dysplasia (right humerus, femur, tibia, skull), precocious puberty and café au lait skin spots, diagnosed as MAS with a confirmed heterozygous c.601C>T mutation of the GNAS1 gene. Due to initial bone pain and continuously increasing bone turnover, the patient was treated with iv bisphosphonates for 4 years. We used pQCT to estimate bone strength parameters at the site of fibrous dysplasia lesion of the right tibia (38% of tibia length) vs the same site of the left (healthy) tibia at baseline and after treatment. A Stratec XCT-2000 scanner was used (Stratec Medizintechnik, Pforzheim, Germany) and we specifically assessed for the 38% site cortical BMC (Cort_CNT), cortical BMD (Cort_DEN), cortical area (Cort_A),cortical thickness (Cort_THK) and Stress Strain Index (SSI) as an indicator of bending/torsional strength.

Results

At baseline all parameters were lower at the right (lesional) tibia: Cort_DEN (right 916.53 vs left 1154.47 mg/cm³), Cort_CNT (0.78 vs 2.65 gr/cm), Cort_A (85 vs 230.25 mm2) , Cort_THK ( 0.99 vs 4.76 mm), SSI (941 vs 1110.35 mm3). All parameters increased significantly after 4 years of therapy at both legs with maximal increases at the lesional tibia: Cort_DEN (left +10.16% vs right + 13.54%), Cort CNT (+13.9% vs +34.6%), Cort_A (+3.14% vs +19.7%), Cort_THK (+4.2% vs +19.19%), SSI (+16.77% vs +26.4%).

Conclusions

1) With 3- dimensional densitometry we can actually measure the loss of cortical bone and derived strength of lesional sites in MAS 2) All bone strength parameters improved with iv bisphosphonates. P QCT, where applicable, is an easy, safe and accurate method for non invasive monitoring of disease progress.

Authors’ Affiliations

(1)
3rd Pediatric Clinic, University of Athens, “Attikon” University Hospital, Greece
(2)
Bone Metabolic Unit, 1st Orthopedic Clinic, University of Athens ,"Attikon" University Hospital, Greece

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