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Bone Abstracts (2019) 7 P156 | DOI: 10.1530/boneabs.7.P156

1Interdisciplinary Cystinosis Clinics, iSPZ, Dr. von Haunersche Kinderklinik, LMU Munich, Munich, Germany; 2Cystinose Stiftung, Munich, Germany.

Objective: Nephropathic cystinosis is an orphan autosomal recessive lysosomal storage disease characterized by a deficiency of cystinosin, a cysteine transporter protein, encoded by CTNS. As a consequence of the disease cystine crystals accumulate leading to tissue damage, primarily in kidney and cornea. With improved medical care, new challenges like skeletal complications are a matter of concern. Only few data are available dealing with bone development. The aim of our study is to gain more information on bone density and geometry in these patients.

Methods: In forty-one patients (24 males, 17 females) with genetically proven nephropathic cystinosis a standard evaluation was performed including history, physical examination, biochemistry, grip strength and imaging studies. Bone mineral density (BMD), bone geometry and muscle cross sectional area were measured using peripheral quantitative computed tomography (pQCT, XCT 2000). We compared results with age-and gender-specific reference data.

Results: Mean age at pQCT evaluation was 22.5±9.79 (range 6.6–39.6). Patients mean z-scores for height −1.98±1.50, weight −1.85±1.20, ulnar length −1.99±1.39 and BMI −1.10±1.28 were significantly reduced (P<0.01). In all, mean z-scores for trabecular −0.10±1.65 and cortical BMD −0.38±1.69 were within normal ranges. However, medullary cross sectional area was normal (−0.18±1.23), together with a reduced total CSA (−1.38±1.22), cortical CSA (−2.33±1.05) was markedly reduced (P<0.01). After adjustment for height, this mismatch was even more pronounced. Muscle CSA and strength strain index (SSI) were normal for patient’s height, however, grip strength z-score reduced with −1.81±1.13 (also after considering ulnar length). Grip strength z-scores correlated with cortical CSA z-scores (r=0.48) and SSI-z-scores (r=0.45) (P<0.01).

Conclusion: In this study population, bone density parameters were within the normal range, but bone geometry was altered, leading to a thinner cortex with impact on bone stability. Muscle weakness as expressed by lower grip strength might be causative and therefore a matter of possible treatment opportunities with a long-term effect on quality of life.

Disclosure: The authors declared no competing interests.

Volume 7

9th International Conference on Children's Bone Health


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